This topic entails a detailed discussion, but in summary Allah said: “And if, when they had wronged themselves, they had but come unto thee and asked forgiveness of Allah, and asked forgiveness of the messenger, they would have found Allah Forgiving, Merciful” (4:64). It is clear that the intercession of the Prophet (peace be upon him and his progeny) is one of the causes of divine mercy and forgiveness, and there is no evidence that this is limited to his life, especially with the traditions narrated from him that indicate that he replies to our salutations and greetings to him after his death; so just as salutations reach him after his death, so do our requests for his intercession.
