Is the phrase: "صلى الله عليه وسلم" (may Allah bless him and grant him peace) an innovation of the Hadith scholars, or does it have a basis in the practice of the Salaf and the Companions? And is it sufficient and does one receive reward for it as a prayer upon the Prophet (may Allah bless him and grant him peace)?

"Salat upon the Prophet (peace be upon him) is a great act of worship, and it is prescribed to do it frequently, for he (peace be upon him) said: 'Indeed, whoever sends salat upon me once, Allah sends salat upon him tenfold thereby.' The phrase 'sallallahu alayhi wa sallam' (peace and blessings of Allah be upon him) is in compliance with the words of Allah the Almighty: 'O you who have believed, pray for him and greet him with a [proper] greeting.' (Quran 33:56). Salat upon him is sufficient in any form that conveys the intended meaning."