What has been reported from ‘Amir bin Sa’d bin Abi Waqqas, from Sa’d from the Prophet (sallallaah alaihi wasallam) also gives evidence to this. The Prophet (sallallaahu alaihi wasallam) gave something to a group of men but left one of them out. So Sa’d said to him, "You gave to them yet you left him out? By Allaah I consider him to be a Believer!" The Messenger of Allaah (sallallaahu alaihi wasallam) said, "Or a Muslim?!"

So he differentiated between Islaam and Imaan.

And we already mentioned that Imaan is a term that signifies all of the acts of obedience and that Islaam is a term that signifies the two testimonies along with the ease of the heart (i.e. its acceptance). So when it is like this then it is obligatory to differentiate between them.

Issue: [Excepting oneself from having perfect Imaan, Istithnaa]

And is disliked for the one who has acquired Imaan that he should say, ‘I am a believer in truth!’ or ‘I am a [true] believer in the sight of Allaah’. Rather he should say, ‘I hope I am a beliver’ or ‘I am a believer if Allaah wills’ or ‘I believe in Allaah, His Angels, Books, and His Messengers’. And none of this is from the angle of doubtfulness in his Imaan, but it is from the aspect that he cannot be absolutely sure that he has fulfilled every single thing with which he has been order and has left everything that he has been forbidden from. This is in opposition to the one who says that when a person knows from himself that he is a believer, it is permissible for him to say ‘I am a believer in truth!’

And the evidence for the impossibility of making this absolute claim [of perfect Imaan] and the necessity of making exception (istithnaa) is the consensus, ijmaa’, of the Salaf.

It was said to Ibn Mas’ud – may Allaah be pleased with him: "This person claims that he is a Believer? He replied, "Ask him whether he is in Paradise or in Hellfire?" So they asked him and he replied, "Allaah knows best". So Abdullaah [Ibn Mas’ud] said to him, "If only you had entrusted the affair of this life as you have entrusted the affair of the Hereafter [to Allaah]!

And because it has already been established that Imaan is characterised by all the acts of obedience and the abandonment of the prohibited matters, then in that situation a person cannot be resolute that he as fulfilled all that is binding upon him and has avoided all that has been prohibited to him. Therefore, it is no possible for him to know that he is a Believer who is deserving of reward.