If he says, “I was in a state of ritual impurity,” we say: You are now in a state of purification. If he says, “I was in a state of purification,” we say: You are now in a state of ritual impurity.

For example, a man is certain that he remained in a state of ablution from the dawn prayer until sunrise. An hour after sunrise, he wishes to pray the forenoon prayer, so he says: “I am certain that, from after sunrise until now, I both invalidated my ablution and performed ablution, but I do not know which occurred first.” We say: You are now in a state of ritual impurity.

But if he says: “I am certain that after the dawn prayer I invalidated my ablution, and that after sunrise I both invalidated my ablution and performed ablution,” we say: You are now in a state of purification …

The reasoning is that he is certain that the former state ceased and was replaced by its opposite, but he doubts whether that opposite state has continued; and the basic presumption is that it remains.

Thus, in the first case, he is certain that he was in a state of ablution until sunrise; then he is certain that he invalidated it thereafter; but then he doubts whether that state of ritual impurity ceased or not. He is therefore told: You are in a state of ritual impurity, because the basic presumption is that the ritual impurity of which you are certain remains. The same applies in similar cases.

If he is certain that both purification and ritual impurity occurred, but does not know which came first and does not know what his state was before them both, he must perform ablution, because there is no established state upon which a ruling can be based. This is the established position of the school.

Some scholars said that ablution is required in all cases (1).