Musnad Abi Ya'la 574 — when the Messenger of Allah ﷺ began the prayer

It is narrated from Sayyiduna Ali (may Allah be pleased with him) that when the Messenger of Allah (peace and blessings be upon him) began the prayer, he would say the takbir (al-tahrimah), and then recite this supplication: 'Wajjahtu wajhiya lilladhi fatara al-samawati wa al-arda hanifan wa ma ana min al-mushrikin, inna salati wa nusuki wa mahyaya wa mamati lillahi rabbi al-'alamin, la sharika lahu, wa bi dhalika umirtu wa ana awwalu al-muslimin. Allahumma anta al-maliku la ilaha illa anta, anta rabbi wa ana 'abduka, zalamtu nafsi, wa'taraftu bi dhanbi, faghfir li dhunubi jami'an, la yaghfiru al-dhunuba illa anta, wahdini li ahsani al-akhlaqi la yahdi li ahsaniha illa anta, wasrif 'anni sayyi'aha, la yasrifu 'anni sayyi'aha illa anta, labbayka wa sa'dayka, al-khayru kulluhu fi yadayka, wa al-sharru laysa ilayka, inna bika wa ilayka, tabarakta wa ta'alayta, astaghfiruka wa atubu ilayka' (I have turned my face, as one inclining to the truth, towards the One who created the heavens and the earth, and I am not of the polytheists. Indeed my prayer, my sacrifice, my living and my dying are for Allah, the Lord of the worlds; He has no partner, and with this I have been commanded, and I am the first of those who submit. O Allah, You are the King; there is no god but You. You are my Lord and I am Your servant. I have wronged myself and I confess my sin, so forgive all my sins, for none forgives sins but You. Guide me to the best of character; none guides to the best of it but You. And turn away from me its bad; none can turn away its bad from me but You. Here I am at Your service, seeking Your favour; all good is in Your hands, and evil cannot be attributed to You. Our existence is from You and to You is our return. You are most Blessed and most Exalted. I seek Your forgiveness and I turn to You in repentance). And when he (peace and blessings be upon him) bowed (in ruku'), he would say: 'Allahumma laka raka'tu, wa laka aslamtu, wa bika amantu, khasha'a laka sam'i, wa basari, wa 'izami, wa mukhkhi, wa 'asabi' (O Allah, to You I have bowed, to You I have submitted and in You I have believed; my hearing, my sight, my bones, my brain and my nerves are humbled before You). And when he (peace and blessings be upon him) raised his head from bowing, he would say: 'Sami'a Allahu liman hamidahu, rabbana laka al-hamdu mil'a al-samawati, wa mil'a al-ardi, wa mil'a ma shi'ta min shay'in ba'du' (Allah hears the one who praises Him. Our Lord, to You belongs all praise, filling the heavens, filling the earth, and filling whatever else You will). Then when he (peace and blessings be upon him) prostrated, he would say: 'Allahumma laka sajadtu, wa laka aslamtu, wa bika amantu, sajada wajhiya lilladhi khalaqahu wa sawwarahu, fa ahsana suwarahu, wa shaqqa sam'ahu wa basarahu, fa tabaraka Allahu ahsanu al-khaliqin' (O Allah, to You I have prostrated, to You I have submitted and in You I have believed; my face has prostrated to the One who created it and fashioned it, then made its form excellent, and opened its hearing and its sight; so blessed is Allah, the best of creators). Then when he (peace and blessings be upon him) gave the salam (at the end of the prayer), he would say: 'Allahumma ighfir li ma qaddamtu wa ma akhkhartu wa ma asrartu wa ma a'lantu, wa ma anta a'lamu bihi minni, anta al-muqaddimu wa anta al-mu'akhkhiru, la ilaha illa anta' (O Allah, forgive me what I have done before and what I have done after, what I have done in secret and what I have done openly, and that which You know better than I do. You are the One who brings forward and You are the One who puts back; there is no god but You).