If it is imagined to him that he has broken his wudu in it, and the evidence is that certainty of purity is not removed except by certainty of impurity, and that the prayer is not invalidated by doubt regarding impurity until the one praying is certain of impurity.

Sayyiduna Abdullah bin Zaid (may Allah be pleased with him) narrates that I asked the Messenger of Allah (peace and blessings be upon him) about a person who feels something during prayer. The Messenger of Allah (peace and blessings be upon him) said: "He should not break his prayer until he hears a sound or perceives a smell."