It is mentioned in books that a person in Basra used to write
the name of the Prophet (s.a.w.a.) but did not write salawaat
after it. Soon his fingers developed a wound and this progressed to such an extent that his fingers fell off.
In another similar episode it is mentioned about a pious man
who was busy in worship and fasting in the days and nights.
He says that I used to write the name of the Prophet (s.a.w.a.)
but not write salawaat after it till one night I saw the Holy
Prophet (s.a.w.a.) in my dream. He appeared to be in a state of
annoyance and anger. He spoke to me saying that when you
write my name, why don’t you write salawaat after it? I woke up fearful from my dream and decided that henceforth
whenever I would write the name of Holy Prophet (s.a.w.a.), I
would also write – Sallallaho Alaihe Wa Aalehi Wa Sallam
(s.a.w.a.) after it. After a period of time, I once again saw the
Prophet (s.a.w.a.) in my dream. He looked at me with merciful
eyes and said, you have started writing salawaat after my
name. Whenever you hear my name or write it, then you
should follow it with the words – Sallallaho Alaihe Wa Aalehi
Wa Sallam (s.a.w.a.)
Ref : Fazila e Salawaat