Sahih Muslim 911
صحيح مسلم#911SahihAbu Humaid as-Sa'idi reported:They (the Companions of the Holy Prophet) said: Apostle of Allah, how should we bless you? He (the Holy Prophet) observed: Say:" O Allah! bless Muhammad, his wives and his offspring as Thou didst bless Ibrahim, and grant favours to Muhammad, and his wives and his offspring as Thou didst grant favours to the family of Ibrahim; Thou art Praiseworthy and Glorious
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 4:73