It is narrated from Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) that when he (peace and blessings be upon him) began the prayer; then the full hadith was mentioned. In it is that when he (peace and blessings be upon him) bowed he said: 'Allahumma laka raka'tu, wa bika amantu, wa laka aslamtu, khasha'a laka sam'i wa basari wa 'azmi' (O Allah, to You alone I have bowed, in You I have believed, and to You I have submitted; my hearing, my sight and my bones are humbled before You). The narrator said: I think he (peace and blessings be upon him) also said: 'wa mukhkhi wa 'asabi' (and my brain and my sinews).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2563