All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
The matter is as we mentioned in Fatwa 91020 that this statement is not considered an act of Kufr [an act that takes a person out of the fold of Islam] because whoever says: "O Prophet of Allaah, ask Allaah to do such and such for me.", he did not associate anything to Allaah, but he wanted to intercede with the supplication of the Prophet after his death. This is something that is not legislated in religion and that is why we mentioned that it is not permissible and that it is an innovation. We also mentioned the saying of the Prophet : "Whoever introduces an act that is not in accordance with ours (concerning religion), it will be rejected." [Al-Bukhari and Muslim]
Allaah Knows best.