Durood o Salaam on The Final Messenger Muhammad [S.A.W.W] : The Comprehensive lecture given by Maulana Ishaq r.a

Surah Al Ahzab ayat 56 :
Surely, Allah and His angels send blessings to the Prophet. O you who believe, do pray Allah to bless him, and send your Salam (prayer for his being in peace) to him in abundance.