Musannaf Ibn Abi Shaybah

Hazrat Jabir narrates that once Hazrat Sa’d said to a man, “Your prayer is not valid.” That man mentioned this to the Prophet (peace and blessings be upon him) and said, “Sa’d has told me that my prayer is not valid.” The Prophet (peace and blessings be upon him) asked Hazrat Sa’d, “Why did you say this?” He replied, “Because while you were delivering the sermon, he was talking.” The Prophet (peace and blessings be upon him) said, “Sa’d is right.”