Musannaf Ibn Abi Shaybah

Hazrat Ibn Abbas (may Allah be pleased with them both) narrates that sometimes Satan puts whispers into a person during prayer in order to break his prayer. When the servant becomes troubled, he (Satan) blows on his buttocks. Therefore, until a sound is heard or a smell is perceived, do not break the prayer. In the same way, he comes and touches his private part, and the person thinks that something has exited from him; so he should not break his prayer until he is certain.