It is narrated from Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) was asked about a man who imagines during his prayer that his ablution (wudu) has been broken, though he has done nothing. The Messenger of Allah (peace and blessings be upon him) said: "Satan comes to one of you while he is in his prayer, until he opens his seat, then makes him imagine that his ablution has been broken though he has done nothing. So when one of you feels that, let him not leave the prayer until he hears its sound with his ear or perceives its smell with his nose."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 11507