Sayyiduna Ka'b bin Ujrah (may Allah be pleased with him) narrates: We said, O Messenger of Allah (peace and blessings be upon him)! We have come to know how to send peace upon you, but how should we send blessings (salat) upon you? The Prophet (peace and blessings be upon him) said: You should say: "O Allah! Send blessings upon Muhammad and upon the family of Muhammad as You sent blessings upon Ibrahim and upon the family of Ibrahim. Surely, You are Praiseworthy, Glorious. And send blessings upon Muhammad and upon the family of Muhammad as You sent blessings upon Ibrahim and upon the family of Ibrahim. Surely, You are Praiseworthy, Glorious."
Hadith Referenceصحیح ابن حبان / كتاب الصلاة / 1957
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - «صفة الصلاة»، «صحيح أبي داود» (896): ق.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح على شرطهما، الحكم: هو ابن عتيبة.