The aqidah of the Salaf with respect to Eemaan is summarized as:

• Eemaan is belief, speech and action, all of these enter into Eemaan and are from the reality of Eemaan. Thus, holding the belief that "Muhammad is the Messenger of Allaah" or "the Qur'an is the speech of Allaah" is Eemaan, and the feeling of love in the heart for Allaah, or hope or fear is Eemaan, and testifying "None has the right to be worshipped except Allaah alone" is Eemaan and saying "Subhaanallaah", or commanding someone "Fear Allaah and do not backbite" is Eemaan, and removing something harmful from the floor or performing prayer is Eemaan, and not stealing, or backbiting, and withholding one's limbs from falling into these actions is Eemaan. The outward actions of Eemaan are not merely the "fruits" and "consequences" of Eemaan as the Murji'at ul-Fuquhaa say, rather they are Eemaan itself.
• Eemaan increases with obedience and decreases with disobedience and it is not just a single indivisible entity that does not admit to increase, decrease - such that if some of it goes all of it goes (in the view of the Khawaarij and Mu'tazilah) or such that none of it goes no matter what actions one does (the Murji'ah) - as [in the erroneous view of both factions], Eemaan is just a single indivisible entity.
• It is permissible make an exception (al-istithnaa) for one's faith by saying "I am a believer, if Allaah wills", out of a) avoiding self-praise, and b) uncertainty about one's future actions and what one will die upon.
• kufr occurs by belief, speech and action and is not restricted to juhood and istihlaal only. Thus, a person becomes a disbeliever through a belief held (speech of the heart), a feeling, emotion harbored in the heart (pride, arrogance, hatred and so on [which is the heart's action]), a statement made by the tongue, or an action performed by the limbs.

And inshaa'Allaah these affairs will be documented and explained in future articles from the speech of the Salaf past and present. For now, on the subject of kufr (the opposite of eemaan) this is a reproduction of an almost ten-year old article (July 2000), with some additions:

Kufr (disbelief) Can Occur Without Istihlaal or Juhood

Amongst the actions of kufr are those for which it is not necessary that a person make istihlaal of them (i.e. declare them to be lawful as a matter of belief) before his action is considered major disbelief that expels from the fold of Islaam.

Shaikh ul-Islaam Ibn Taymiyyah said in "As-Saarim al-Maslool" (p.514):

And it is necessary for it to be known that the statement that 'the disbelief of the one who reviled (Allaah, the Messenger or the religion) is only disbelief because he made istihlaal of his act (i.e. declared this revilement to be lawful)' is a repugnant mistake and very great error...and this is from numerous angles...

When a person reviles the Messenger (sallallaahu alaihi wasallam) or throws the Qur'an into some filth, or kicks the Qur'an without compulsion, heedlessness, or out of error for example, then it is not a requirement nor a condition that he considers or declares this act to be lawful (istihlaal) as a matter of belief before this act is considered kufr and takfir is made upon him. Rather it is sufficient to known that he intended his act and did it wilfully, meaning he chose to do the act, desiring it, intending it, not being under compulsion or the likes.

As for Istihlaal (having the belief that something that Allaah has made unlawful is lawful), then it is of two types, that which is related to action, and that which is related to belief.

Shaikh Ibn Uthaimeen said in "Liqaa Baab al-Maftoo" (no. 1200):

Istihlaal is that a person believes that something that Allaah has made unlawful is lawful. As for Istihlaal of action, then we need to observe: If this Istihlaal (is related to something) that expels from the religion then a person becomes a disbeliever and apostate by it. So for example, if a person worked with usury (i.e. took or gave usury) without believing in its lawfulness, yet he persists in working with it, then such a one does not become a disbeliever because he did not declare it to be lawful. However, if he said, "Usury is lawful" and he intends by this the usury that Allaah has declared unlawful, then he becomes a disbeliever, since he is a denier (mukaddhib) of Allaah and His Messenger (sallallaahu alaihi wasallam). So in this circumstance, Istihlaal would be that of action and also that of belief, with his heart. However, the Istihlaal in action, we need to look at the action itself, is it something which in and of itself, expels from the religion or not? And it is known that consuming interest does not make a person a disbeliever, rather it is one of the major sins. However, if a person prostrated to an idol, then he becomes a disbeliever. Why? Because this act itself expels from the religion. This is the principle, however it is necessary for us to observe another condition, and this is that the person who made something lawful (by istihlaal) is not excused due to ignorance, for if he is excused due to ignorance, then he does not become a disbeliever.

So Istihlaal is of two types, that which is related to action and that which is related to belief. That which is related to belief is disbelief in all circumstances, regardless of whether this istihlaal was in relation to something that only reaches the level of minor kufr or something reaching the level of major kufr. For example, if one made fornication lawful as a matter of belief, or drinking and likes then he is a disbeliever. Likewise, if he made reviling the Messenger (sallallaahu alaihi wasallam) or reviling the religion to be lawful, then regardless of whether he did the act or not, then he becomes a disbeliever by this istihlaal. So this type of istihlaal is disbelief (kufr) which expels from the religion, in all circumstances.

As for the istihlaal that is related to action, and this merely means that a person commits the act - in other words he makes it lawful for himself in terms of his action only, in the sense that he performs the act, allowing and permitting himself (from his choice) to fall into it - then in such a situation one must look at the action he committed. Is it something that does not reach the level of major kufr? Such as fornication, stealing, gambling and the likes. In this case he is not a disbeliever by this Istihlaal of action. However, if it is an act (or statement) which expels from the religion, such as prostrating to an idol, then he becomes a disbeliever by this Istihlaal of action.

And this is the principle concerning Istihlaal in the view of our Ulamaa. In light of this, the well known statement of Imaam at-Tahaawi: "We do not declare someone a disbeliever on account of a sin he committed, so long as he does not declare it lawful." Is subject to the above clarification and qualification and is not taken absolutely.

With respect to Juhood (wilful rejection), then Imaam Abu Ja'far at-Tahaawi said "A servant does not exit from Imaan except by denial (juhood) of that which brought him into it." Shaikh Ibn Maani' wrote in his brief commentary on it:

He intends to refute the Khawarij and the Mu'tazilah by this, those who expel such a person from Imaan on account of a sin that he commited

And Shaikh Ibn Baaz said, further clarifying this on his commentary on this text:

This absolute generalisation [of at-Tahawi] requires further examination. For a disbeliever enters into Islaam by the two testifications if he had not uttered them previously, and if he was one who had uttered them, then he will enter into Islaam (again) after repenting from what had necessitated his disbelief. And a person can exit from Islaam without showing Juhood (denial, rejection) for many reasons which the people of knowledge have explained in the discussion of the rulings pertaining to the apostate. Amongst them: when he reviles Islaam or the Prophet (sallallaahu alaihi wasallam), or mocking Allaah, His Messenger or His Book or anything from His Legislation - free is he of imperfection - due to his saying,

Say: Was it in Allaah, His Signs and His Messenger that you were mocking? Do not seek to make excuses, for you have disbelieved after having had faith!" (at-Tawbah 9:65-66).

And also amongst such (actions) are worshipping idols, calling upon the dead, seeking help from them, seeking assistance from them and other such things. Therefore, whoever directs any of these (acts of worship) to other than Allaah, such as to idols, the angels, the jinn, those in the graves and others from the creation then such a one has committed Shirk with Allaah and has not actualised the meaning of "Laa ilaaha ilallaaha". All of these matters cause a person to exit from Islaam by unanimous agreement of the Muslims, and they are not from the matters of Juhood (denial, rejection). The proofs for these matters are well known from the Book and the Sunnah, and the Scholars have mentioned them in the chapters related to the ruling upon the apostate, so refer back to them if you will. And in Allaah lies success.

Just like our discussion with Istihlaal above, there are some actions for which Juhood, that is denial or rejection, is not a requirement for an action to be considered as major disbelief (kufr akbar) and what expels from Islaam. Rather such actions, in and of themselves are major disbelief and expel from Islaam. However, it is worth noting here, for the sake of completeness, that some of the Scholars have said that all of those matters which expel from Islaam, then the basis of all of that is Juhood (denial, rejection) of what the Messenger (sallallaahu alaihi wasallam) came with, from the consideration of the angle of the necessity of the hujjah being established upon a person before he is judged a kaafir.

Shaikh 'Abdur-Rahmaan bin Naasir as-Sa'dee said in "Manhaj us-Saalikeen" (p.112):

Chapter: The Ruling upon the Apostate. "The apostate, murtad, is the one who exits from Islaam and enters into disbelief on account of an action, statement, a belief or doubt. And the Scholars - may Allaah have mercy upon them - have mentioned the specific detail and explanation of the matters by which a servant leaves Islaam. And all of them have their basis in the rejection, jahd, of what the Messenger (sallallaahu alaihi wasallam) came with, or rejection, jahd, of some of it. So the one who apostatizes should be asked to repent during the course of three days. If he repents and returns, then fine, otherwise he is to be killed with the sword.

If one was to consider this statement to mean that the acts of kufr, such as those mentioned above in the statement of Imaam Ibn Baaz are not to be considered as major disbelief unless they are accompanied with Juhood and all return back to juhood, then this is an erroroneous understanding of what as-Sa'dee has said. Rather such acts in and of themselves are major disbelief. Hence, if the latter part of the above statement of as-Sa'dee is taken in isolation, it leads to a faulty understanding. But the Shaykh at the beginning clearly stated that a person leaves Islaam through a belief, statement, action or doubt. And regarding what he said after this, then it means that a person becomes an apostate and the hadd punishment applied after the proof has been established (iqaamat ul-hujjah) and the person does not repent or desist or recant from his act or statement of kufr, but persists in choosing death over repentance, then his indicates his "jahd" (rejection) of what the Messenger (alayhis salaam) came with, alongside the fact that the act that he initially committed was major kufr on its own, independently, which negated his Eemaan. Then this is in conformity with the principle of takfir concerning those who fall into these acts which is that the proof is established against them and their repentance is sought before making the takfir of the individual and applying whatever follows on from it. However, this does not mean that kufr is restricted to mere "juhood", so whoever understood that from the statement of as-Sa'dee is in error.

Shaikh Muhammad bin Abdul-Wahhaab said, as quoted in "Aqidat us-Shaikh Muhammad bin Abdul-Wahhaab" (p.208) of Shaikh Salih al-Ubood:

[The apostate] is the one who has disbelieved according to the consensus (ijmaa) of the Muslims, and he is the one upon whom the proof has been established. The one upon whom the proof has not been established is not to be declared a disbeliever.

In summary, we say that the amongst the actions of kufr are those which do not require istihlaal of the heart or juhood of the heart be present for them to be considered actions of major kufr which expel from Islaam. It is not required a person hold as his belief that mocking the Messenger (alayhis salaam) or reviling Allaah, or the religion, or prostrating to an idol is "lawful" before his act is deemed to be kufr (that expels from Islaam) after his performance of it, for it is major kufr regardless. Similarly it is not required that he made "juhood" (denial, rejection) of the prohibition of these actions of major kufr before these actions are considered to be major kufr in and of themselves, for they are major kufr regardless.