Hazrat Aboo Bakr Siddeeq (Allaah be pleased with him) says,

“Sending Durood upon the Holy Prophet [Sallal Laahu Alaieh Wa Sallam] wipes away the sins just like cold water extinguishes fire. And sending salutations upon the Holy Prophet [Sallal Laahu Alaieh Wa Sallam] is better deed than freeing a slave.”

(Shifaa Shareef, 2, Pg 61)