He was unsure whether His Clothes had been polluted by Something while He was praying
Question :
If the Imam is unsure whether his clothes have become polluted, and he does not leave the prayer, since it is only a doubt, then when he finishes praying, he finds some filth on his garment, what is the ruling? And should he leave the prayer in this situation, due to only a doubt, or should he wait until he has prayed?
Answer:
If the worshipper is in doubt as to the presence of some pollutant on his garment while praying, it is not permissible for him to abandon the prayer, whether he is the Imam, or a worshipper being led by the Imam, or he is praying alone. He must complete his prayer, and if he finds after that, that there is some pollutant on his garment, there is no obligation on him to make up for it, according to the most authoritative opinion, because he was not aware of its presence until after the prayer. It has been reported authentically from the Prophet that he removed his shoes during the prayer when Jibril informed him that there was some filth on them, and he did not repeat the first part of the prayer, instead, he continued to pray. And the giver of success.
Source:
Ibn Baz
Fatawa Islamiyah, Vol. 2 Pages 40