What is the ruling on supplicating with, "O Allah, send prayers upon our Master Muhammad, the key to the treasuries of Your mercy; O Allah, open for us thereby what has been closed to us"?

The best forms of sending blessings upon the Prophet, peace and blessings be upon him, are the forms he taught his companions, known as the Abrahamic Prayer (Salah al-Ibrahimiyyah). Sending blessings upon the Prophet in the form "O Allah, bless our master Muhammad, the key to the treasuries of Your mercy" is permissible if "key" is intended to mean some treasuries of His mercy, such as the gates of Paradise. As for the statement "O Allah, through him open for us what has been closed to us," this is seeking intercession through the person of the Prophet, peace and blessings be upon him, which is prohibited according to the preponderant opinion of the scholars.