And whoever used more than three even stones for istinja and did not use an odd number, then he will not be sinful because he has left a non-obligatory, recommended, and superior act, not an obligatory one.

It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Prophet Muhammad (peace and blessings be upon him) said: "When any one of you performs istinja with stones, he should use an odd number (of stones). Indeed, Allah is Odd and loves odd numbers. Do you not see the seven heavens, the seven earths, and the seven circuits of Tawaf? (i.e., all these are odd.)" In this way, he mentioned several things.