One day Hazrat Jibrael came to the Holy Prophet (s.a.w.a.) and
said, O Holy Prophet! Today I have witnessed a strange sight.
While passing by the mountain of Qaff, I saw an angel who I
have seen earlier bearing a lofty position in the skies. He used
to sit on a throne of light. Seventy thousand angels were
deputed to serve him. Every breath from him became the cause of creation of angels. However today I saw him in a dejected
and aggrieved state. He replied that when the Holy Prophet
(s.a.w.a.) was returning from Meraj, he was negligent in
offering my respects to the Prophet. Due to this, Allah revoked
his lofty status and threw him on the earth. The angel requested
Hazrat Jibrael to pray for his forgiveness. When Hazrat Jibrael
prayed for him, Allah revealed to him that he should ask the
fallen angel to send Salawaat upon Mohammad (s.a.w.a.) and
his family (a.s.) in order that his sin should be forgiven. When
he did so, Allah (s.w.t.) restored his wings and his status after
which he flew to the sky
Ref : Fazila e Salawaat