It is narrated from Sayyiduna Abu Sa'id Khudri (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) led the prayer and (during the prayer) removed his shoes, so the people also removed their shoes. When the Prophet (peace and blessings be upon him) finished, he asked: "Why did you people remove your shoes?" They said: "O Messenger of Allah! We saw you removing your shoes, so we also removed ours." The Prophet (peace and blessings be upon him) said: "Jibril (peace be upon him) came to me and informed me that there was impurity on my shoes. Therefore, when any one of you comes to the mosque, he should turn his shoes over and check them. If he sees any impurity on them, he should clean it off with the ground and then pray in them."