Importance Of Saluting Prophet Muhammad And His Household

Amir al-Muminin (the Commander of the Faithful) (A.S) said: do not recite any prayer unless you say this at its beginning: 

صَلِّ عَلَى مُحَمَّدٍ وَآلِ مُحَمَّدٍ وَافْعَلْ بِي كَذَا وَكَذَا. 

Bless Muhammad and his Household and accept my prayer (and ask for your need). 

Also, he always did this and he was asked about it and replied: whenever the prayer is accompanied by a salute, it is accepted, and God the Almighty is embarrassed if His servant asks for two things he needs and He accepts one and leaves the other one unaccepted.