عَنْ أَبِي مُوسَى الْأَشْعَرِيِّ رَضِيَ اللَّهُ عَنْهُ قَالَ: لَقَدْ ذَكَّرَنَا عَلِيُّ بْنُ أَبِي طَالِبٍ رَضِيَ اللَّهُ عَنْهُ صَلَاةً كُنَّا نُصَلِّيهَا مَعَ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ إِمَّا نَسِينَاهَا وَإِمَّا تَرَكْنَاهَا عَمَدًا يُكَبِّرُ كُلَّمَا رَكَعَ وَكُلَّمَا رَفَعَ وَكُلَّمَا سَجَدَ
Sayyiduna Abu Musa Ash’ari (may Allah be pleased with him) says: Sayyiduna Ali ibn Abi Talib (may Allah be pleased with him) reminded us of the prayer which we used to perform with the Messenger of Allah (peace and blessings be upon him), either we had forgotten it or deliberately abandoned it. Sayyiduna Ali (may Allah be pleased with him), when he would bow (in ruku’), rise (from ruku’), and prostrate (in sujood), he would say Allahu Akbar.