The reasoning is that he is certain that two states occurred, and these two states are opposites, yet he does not know which of them came first. Thus, he does not know which one superseded the other, so they cancel each other out. Since he is certain that his original state ceased, he must perform ablution as a precaution, just as when he does not know his state before the two events.

The view that ablution is obligatory is more cautious. For instance, after sunrise, he is certain that he invalidated his ablution and performed ablution, but does not know which of the two came first. It is possible that he renewed his ablution and then invalidated it, in which case he must now perform ablution. Since this possibility exists, he cannot escape doubt except by performing ablution.

If this ablution is in fact obligatory, then he has fulfilled it; otherwise, it is sunnah. The jurists, may Allah have mercy on them, said: When doubt becomes strong, it is recommended to perform ablution so that one may attain purification with certainty (1).

In summary, there are four cases:

The first: that one is certain of purification but doubts whether ritual impurity occurred.

The second: that one is certain of ritual impurity but doubts whether purification occurred.

The third: that one is certain that both occurred, but does not know which came first, while knowing his state before them.

The fourth: that one is certain that both occurred, but does not know which came first, and does not know his state before them. The ruling for each of these cases has already been explained …

Through this classification and others like it, the meticulous discernment of the people of knowledge becomes clear: hardly any issue can arise in one’s mind without their having mentioned a ruling for it. This is part of