(a) Sayyiduna Abu Mas'ud al-Badri (may Allah be pleased with him) states: If I were to offer even one prayer in which I did not send blessings upon the Prophet (peace and blessings be upon him) and the family of Muhammad (peace and blessings be upon him), I would consider that prayer incomplete.
(b) Jabir al-Ju'fi is alone in narrating this hadith, and he is a weak narrator. The hadiths on this subject that have passed here and in the chapter on the description of the prayer are sufficient. And success is from Allah.
(c) It has been narrated to us from Imam al-Sha'bi (may Allah have mercy on him) that whoever does not send blessings upon the Prophet (peace and blessings be upon him) in the tashahhud should repeat his prayer, or he said: his prayer will not suffice.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3969