, let him set aside his doubt and proceed on the basis of what he knows for certain, then perform two prostrations before the concluding salutation. If he has prayed five units, these two prostrations will make his prayer even; if he has prayed exactly four, they will serve to humiliate Satan.”

This hadith instructs anyone who doubts and does not know to set aside his doubt. It also commands two prostrations before the concluding salutation.

People have differed in their understanding of his words, “If any of you has doubts.” Some have understood this to mean that anyone who lacks certainty is in doubt, even if he considers one of the two possibilities more likely. Thus, they regarded someone who considered one possibility more likely as being in doubt, even when those praying behind him agreed with him. They instructed him to disregard what he doubted and proceed on the basis of what he knew for certain. They said that the default assumption is that whatever is in doubt has not occurred. They therefore gave unconditional precedence to the presumption that the previous state continues, even when supporting evidence and indications pointed to the contrary, and gave no weight whatsoever to exercising judgment to determine what was most likely correct.

Some of them interpreted the Prophet’s words, may Allah bless him and grant him peace, in the other hadith, “Let him exercise his judgment,” as meaning that he should proceed on the basis of certainty.

Another group said that, if he is leading the prayer, the doubt intended is one in which the two possibilities are equally likely; if he is praying alone, it means what the first group described.

A third group said: Rather, doubt here means that the two possibilities are equally, or nearly equally, likely. When one outweighs the other, however, he should act on the more likely possibility. This is what is meant by exercising judgment. Three positions are reported from Imam Ahmad, corresponding to these three views.

The first is the view of Mālik and al-Shāfiʿī, and the position preferred by many of Ahmad’s followers.