For example, a man has two vessels: one contains purifying water and the other impure water, but he is unsure which is the purifying one. We say: he must avoid both of them.
If he asks, “What should I do when I wish to pray?” we say: Perform dry ablution, because you are unable to use water due to the uncertainty as to which water is purifying and which is impure. Thus, he falls under the saying of Allah, Most High: “And if you cannot find water, then perform dry ablution.” [al-Ma’idah 5:6]
Is it a condition for performing dry ablution that the two waters be poured out or mixed together? There are two views on this (1). This is why the author, may Allah have mercy on him, denied that pouring them out or mixing them is a condition: in refutation of the second view. Otherwise, there would have been no reason for his denial. He therefore said, “Nor is it stipulated …,” in response to those who maintain that pouring out the two waters, or mixing them, is required. This is one view in the madhhab.
They said: He cannot perform dry ablution until he pours out both waters, so that he truly has no water; or until he mixes them, so that their impurity is established with certainty.
It is understood from this that if it is possible to purify one of them with the other, purification is obligatory and there is no need for dry ablution. This is where each of the two vessels contains two qullahs or more: one is added to the other, for the purifying water will purify the impure water once its change has disappeared.
If it is confused with pure water, he performs one ablution using both: one scoop from this vessel and one scoop from that vessel, and he offers one prayer.
His statement, “If it is confused with pure water, he performs one ablution using both: one scoop from this vessel and one scoop from that vessel, and he offers one prayer,” refers to an issue that does not arise according to the view we have deemed correct, since there is no pure water that is not purifying according to the sound view. However, it does arise according to the madhhab, and the meaning of pure water has previously been explained (2).