Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates: Before coming from Habashah, during prayer we used to greet the Prophet Muhammad (peace and blessings be upon him), and he (peace be upon him) would reply to us. When we returned (from Habashah), I greeted the Prophet Muhammad (peace and blessings be upon him) while he was performing prayer, but he (peace be upon him) did not reply to my greeting, so I began to have disturbing thoughts. I sat there until the Prophet Muhammad (peace and blessings be upon him) completed the prayer. Then I said: O Messenger of Allah! I greeted you while you were praying, but you did not reply to my greeting. The Prophet Muhammad (peace and blessings be upon him) said: "Allah, the Exalted, can issue a new command in any matter He wills, and the new command regarding this is that you should not speak during prayer." Sufyan says: Of the narrations we have received from Asim, this is the best among them.