It is narrated from Sayyiduna Abu Humayd As-Sa‘idi (may Allah be pleased with him) that the Companions (may Allah be pleased with them) said: O Messenger of Allah (ﷺ)! In which words should we send blessings upon you? The Prophet (ﷺ) said: “Say like this: ‘O Allah! Send mercy upon Muhammad (ﷺ), upon his wives, and upon his offspring, as You sent mercy upon the family of Ibrahim (peace be upon him), and send blessings upon Muhammad (ﷺ), upon his wives, and upon his offspring, as You sent blessings upon the family of Ibrahim (peace be upon him). Surely, You are Most Praiseworthy, Most Glorious.’”
Hadith Referenceالسنن المأثورة / باب ما جاء في الصلاة على الراحلة / 100
Hadith Takhrijصحیح بخاری احادیث الانبیاء، باب يزفون النسلان في المشي، رقم : 3369، 6369، صحیح مسلم، الصلاة، باب الصلاة على النبي بعد التشهد، رقم : 407۔