Sayyiduna Abu Hurairah (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) said: "Whoever sends blessings and peace upon me once, Allah will send mercy upon him ten times."
(Explanation of Hadith 2806) The meaning of «صلاة» is supplication and peace, blessings, worship, mercies, favors, etc. Qadi Iyad states: Allah Ta’ala will send His mercies ten times upon the one who sends blessings (salat) once, or He will grant him ten times more reward, just as Allah Ta’ala has said: Whoever does a good deed, Allah Ta’ala will grant him tenfold or even more goodness. It should be clear that by «صلاة على النبي» is meant that very salat (blessing) which is recited in prayer or which is mentioned in the ahadith. To say or recite self-invented forms of salat and salam, or to collectively chant “as-salamu alayka ya Rasul Allah” melodiously at the time of prayer or adhan, are reprehensible innovations (bid‘ah qabihah), which neither Allah nor His Messenger have commanded. May Allah Ta’ala grant everyone the ability to follow the Sunnah and to avoid innovation (bid‘ah), Ameen.