Musannaf Ibn Abi Shayba 3:4908

Abu Bakr narrated to us, he said: Hushaym narrated to us, he said: Husayn informed us, he said: I asked Ibrahim about a man who sees blood on his garment while he is in prayer. He said: "If it is a lot, let him cast the garment away from him, and if it is a little, let him proceed in his prayer."