Sayyiduna Ali (may Allah be pleased with him) says: The first prayer we offered was the Asr prayer (or perhaps the translation is: the first prayer in which we performed bowing was the Asr prayer). I said: "O Messenger of Allah! What is this?" He (peace and blessings be upon him) said: "I have been commanded with this."
Al-Bazzar, and al-Tabarani in al-Mu'jam al-Awsat, recorded it; its chain contains a narrator Abu Abd al-Rahim. If he is Khalid bin Yazid, then he is thiqah (trustworthy) and one of the narrators of the Sahih. I have not found Abu Abd al-Rahim mentioned in Mizan al-I'tidal; this person is majhul (unknown).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 1621
Hadith Gradingمحدثین:إسنادہ ضعیف بوجہ جہالتِ راوی
Hadith Takhrij«البحر الزخار مسند البزار ومما روى زاذان عن على بن ابي طالب ، 733 ، المعجم الاوسط للطبراني باب العين ، باب الميم من اسمه محمد 7389 ، أخرجه مسند البزار برقم: 814، وأخرجه المعجم الأوسط للطبراني برقم: 7249»