Addressing the Messenger when sending prayers for him
It is permissible to invoke Allah's Blessings upon the Prophet (peace be upon him) in the second person pronoun as authentically reported in the Hadith about reciting Tashahhud (a recitation in the sitting position in the second/last unit of Prayer) in Salah (Prayer). If a person is asked about something they do not know, they should say, 'I do not know' or 'Allah knows best'. They should not say, 'Allah and His Messenger know best' after the death of the Prophet because he (peace be upon him) does not know what happens to people after his death.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.