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 Can Occur Without Believing in kufr or Desiring It

Amongst the actions and statements are those on account of which a person exits from Islaam and it is not a condition that he desires (yaqsud) to leaves Islaam, or desires to commit kufr or that he believes in the statement of kufr he uttered.

Ibn Hajr said in Fath ul-Baree (12/373):

Amongst the Muslims are those who exit the religion without desiring (qasd) to leave the religion and without choosing a religion other than that of Islaam.

Shaikh ul-Islaam Ibn Taymiyyah as-Saarim al-Maslool (p.178):

And in essence, whoever says or commits that which is disbelief, kufr, disbelieves on account of it, even if he did not desire (lam yaqsud) to become a disbeliever (by the act), since no one desires disbelief except as Allaah wills.

To illustrate this point, a person may prostrate to an idol and this act in and of itself is kufr that expels from the religion. The ruling of takfir may be made upon a person, provided the preventative barriers to takfir are removed (such as ignorance amongst a people who do not know this opposes the deen of the Messengers, faulty ta'weel, compulsion, error, protection of one's life). However, it is not a condition that a person "intended to perform kufr" by this act, before the act is described as being major kufr and before he is judged a with having committed major disbelief and steps taken to establish the hujjah upon him to verify the ruling upon him. This is because the mushriks who worship the dead and make supplication to them, believing that the dead provide for them and protect them, they never "intend to perform kufr" by these acts, rather they consider them to be worship and nearness to Allaah, yet they are the greatest of acts of shirk and apostasy. Thus, it is not necessary that a person "intend" to commit kufr or "intend" to leave Islaam.

To illustrate with another example, a person who mocks and reviles Allaah or the Messenger, it is not required that the person "desired kufr" by his words of mockery or revilement, and neither is it a condition that he "believed (i'taqada) in the correctness or validity of the words he used to make mockery or revilement" before takfir is made of him.

Rather, if he said these words deliberately, intending to say these words, desiring to say these words, then that in and of itself is the kufr that expels from the religion. Thus, there is a difference between "desiring the act" and "desiring kufr". The latter, "desiring kufr" is of no significance and its presence or absence has no bearing on the ruling of takfir (in those cases where the action is major kufr that expels from the religion). If a person desired kufr in his heart, then he would become a disbeliever through that, regardless of whether he performed an act of kufr or not, or uttered a statement of kufr or not. However, the former, "having desired the act", meaning that a person wilfully did the act, then this does have a bearing on the ruling of takfir, for this is related to the preventative barriers and required conditions for the performance of takfir, in the sense that it must be verified that this act did not occur out of compulsion, or error and the likes.

To give another example to make this clearer. Let's say a Muslim is participating in a play in a theater or something, and he is doing it just as a job or just as a pastime, and within the play he has lines which include mockery of the religion or mockery of the Messenger (alayhis salaam). Now, if he said those words, saying those words out of choice as opposed to saying them erroneously (while intoxicated, or out of a mere slip and so on), then irrespective of what his motive is, as long as it is established that he wilfully chose to say those words, desiring to say them, then that is major kufr. And from this example, we can distinguish between what amounts to an operating motive (he is getting paid money to act) and what is established as his qasd (intent, desire) and willful choice for the act. They are two different things. His motive does not play any role in determining whether he fell into kufr or not. It is irrelevant whether he only said it because he wanted money, or because he got involved in the play to pass time, or whatever. All of that is irrelevant. If he said it, choosing to say it, desiring to utter those words of mockery, then that is major kufr. Whether you believed in the correctness of those words, or said them only out of jest (i.e. not seriously) and all of those other similar things are not considered. The only thing is considered where the statement is very clear and not anything but mockery, is whether a person deliberately said them out of choice.

Ibn al-Qayyim said in I'laam ul-Muwaqqi'een (3/63),

It has preceded that the one who uttered, when he found his lost camel, "O Allaah, you are my servant and I am your Lord" erred due to extreme joy and he did not disbelieve by these words, even though he uttered pure and clear kufr. This is because he did not intend to say it. And the one who is compelled to utter kufr, has indeed spoken with a word of kufr, but he does not become a disbeliever since he did not desire to utter this word, as opposed to the one who mocks or jests (about Allaah, the Messenger, or the religion). In this case, such an utterance would necessitate disbelief and divorce, even if he was only joking and fooling around, since he desired to utter these words (qaasidun littakallum bil-lafdh). And even if he was just joking, then this would be no excuse for him, as opposed to the case of the one who is compelled, or who erred, or who was forgetful. Such a one is excused...

Shaikh ul-Islaam Ibn Taymiyyah said in Saarim al-Maslool (p. 524):

Whoever uttered with his tongue a word of disbelief without having any need for it, deliberately saying it, knowing that it is an utterance of disbelief, then he becomes a disbeliever through that both inwardly and outwardly, and we do not make it permissible for it to be said, "It is possible for him to still be a believer inwardly"...

Shaikh ul-Islaam added to the above, in explanation of the verse in Surah Nahl, "Whoever disbelieved in Allaah after his belief, except him who is compelled and whose heart is at rest with Imaan. However, those who open their breasts to disbelief, on them is wrath from Allaah, and theirs will be a great torment" (Nahl 16:106)" - so he said in Saarim al-Maslool (p. 524):

And it is known that he did not intend by the disbelief mentioned here, the disbelief that relates to belief (i'tiqaad) of the heart only, because a man cannot be compelled with respect to this (i.e. his heart cannot be forced to hold a particular belief, even though he may be forced to say it with his tongue). And He excepted the one who is compelled (to disbelief) but did not meant the one who uttered (disbelief) and believed in what he said, because he excepted the one who is compelled...

In other words, only one who utters disbelief under compulsion is excused, as for the one who utters disbelief, then he has disbelieved, irrespective of whether his heart believed in what he said or not, since although a man can be forced to say something with his tongue, he cannot be forced to accept and believe it with his heart, and hence the compulsion being referred to in the verse mentioned above, is the one that is related to the tongue only, in the sense, that he has been forced to say what is kufr out of fear of harm. He did not wilfully choose it. So what is of concern and what count is whether a person willfully chose his action or his words, being under no compulsion, desiring to do this action, or say his words, and then doing it or saying it.

In conclusion, it is not necessarily a condition that when someone utters disbelief, that he also believes in what he uttered for his action to be considered disbelief or for it to be considered that he has fallen into disbelief.