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. He (peace be upon him) said: "He should not leave (the prayer) unless he hears a sound or perceives a smell."
Because certain purity is not nullified by doubt or suspicion; certainty is only nullified by certainty. Therefore, the previously existing certain purity will only be invalidated by certain impurity.
Hadith Referenceصحيح ابن خزيمه / جماع أبواب الأحداث الموجبة للوضوء / 25