Is the so-called Prayer of Gabriel, in which the formula "May God bless Muhammad" is recited and which is said to have certain virtues, authentically reported from the Prophet (PBUH) and his companions, or is it an innovation (bid'ah)?

The virtue of praying upon the Prophet, peace and blessings be upon him, is established in many hadiths. Among its fruits are the easing of distress, the removal of worries, and the fulfillment of needs. Part of its perfection is to dedicate all your prayers to supplication and prayers upon the Prophet, peace and blessings be upon him, so that Allah may suffice you in your worries and forgive your sins. There is no prayer called "Salat Jibreel," but Jibreel brought glad tidings to the Prophet, peace and blessings be upon him, regarding the virtue of praying upon him. For whoever prays upon the Prophet, peace and blessings be upon him, once, Allah will pray upon him ten times.