Abu Hamzah, a man of the Ansar, heard Sayyiduna Zayd bin Arqam (may Allah be pleased with him) say that the first person to pray with the Prophet (peace and blessings be upon him) was Sayyiduna Ali bin Abi Talib (may Allah be pleased with him). He said: I mentioned that to Ibrahim (may Allah have mercy on him), and he rejected it and said: It was Sayyiduna Abu Bakr (may Allah be pleased with him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب اللقطة / 12158