Abu Humaid as-Sa‘idi said that when some people asked Allah's Messenger ﷺ how they should invoke blessings on him he told them to say, “O Allah, bless Muhammad, his wives and his offspring as Thou didst bless Abraham; and grant favours to Muhammad, his wives and his offspring as Thou didst grant favours to the family of Abraham. Thou art indeed praiseworthy and glorious.” (Bukhari and Muslim.)