Bukhari

Hadith Commentary:
The one whom he called a disbeliever (kafir), if he is in reality a disbeliever, then indeed he is a disbeliever; but if he is not a disbeliever, then the one who uttered this statement has himself become a disbeliever.
For this reason, the Ahl al-Hadith have exercised great caution in the matter of declaring someone a disbeliever (takfir). They say: “We do not declare any person of the Qiblah (i.e., any professing Muslim) to be a disbeliever.” However, the later jurists (muta’akhkhirin fuqaha) in their books declare their opponents to be disbelievers over the most trivial matters. The author of al-Durr al-Mukhtar has, with great audacity, recorded this fatwa:
“So may the curse of our Lord, as numerous as the grains of sand, be upon the one who rejects the statement of Abu Hanifah,”
meaning: Whoever rejects any statement of Imam Abu Hanifah, upon him be as many curses as there are particles in the world.
Say, according to this principle, then all the Imams of the religion would be accursed, for they have rejected the statements of Imam Abu Hanifah rahimahullah in many issues.
Even the students of Imam Abu Hanifah rahimahullah themselves differed with him in numerous matters—so, according to the author of al-Durr al-Mukhtar, were they all accursed and rejected?
Some people have considered Imam Abu Hanifah rahimahullah to be a prophet, or, under the verse: اتَّخَذُوا أَحْبَارَهُمْ وَرُهْبَانَهُمْ أَرْبَابًا مِنْ دُونِ اللَّهِ (), have made him into a deity besides Allah.
Imam Abu Hanifah rahimahullah was a scholar of the religion; he erred in many issues—he was not infallible (ma’sum).
This hadith should serve as a lesson for those who, without investigation and merely on the basis of conjecture, declare Muslims to be polytheists (mushrik) or disbelievers (kafir).
(Wahidi)