Ali bin Abi Talib narrated that whenever the Messenger of Allah (ﷺ) would stand for Salat, he would say

“I have directed my face towards the One who has created the heavens and the earth, as a Hanif, and I am not of the idolaters. Indeed, my Salat, my sacrifice, my living, my dying, is for Allah, the Lord of all that exists, without partner, and with this have I been ordered and I am of the Muslims. O Allah, You are the King, there is none worthy of worship except You. You are My Lord, and I am Your slave, I have wronged myself and I admit to my sin, so forgive me all my sins, verily, there is none who forgives sins but You, and guide me to the best of manners, none guides to the best of them except You, and turn away from me the evil of them, none can turn away from me the evil of them except You. Here I am in obedience to You, and in aiding Your cause, and the good, all of it is in Your Hands, and the evil is not attributed to You, I am reliant upon You and ever-turning towards You, Blessed are You and Exalted are You. I seek Your forgiveness and I repent to you (Wajjahtu wajhiya lilladhī faṭaras-samāwāti wal-arḍa ḥanīfan wa mā ana min al-mushrikīn, inna ṣalātī wa nusukī wa maḥyāya wa mamātī lillāhi rabbil-`ālamīn, lā sharīka lahū wa bidhālika umirtu wa ana min al-muslimīn. Allāhumma antal-maliku lā ilāha illā ant, anta rabbī, wa ana `abduka ẓalamtu nafsī wa`taraftu bidhanbī faghfirlī dhunūbī jamī`an, innahū lā yaghfir adh-dhunūba illā ant. Wahdinī li-aḥsanil-akhlāqi lā yahdī li-aḥsanihā illā ant. Waṣrif `annī sayyi’ahā lā yaṣrifu `annī sayyi’aha illā ant. Labaika wa sa`daika wal-khairu kulluhū fī yadaika, wash-sharru laisa ilaik, tabārakta wa ta`ālaita astaghfiruka wa atūbu ilaik).” And when he would bow in Ruku he would say: “O Allah, to You have I bowed, and in You have I believed, and to You have I submitted. My hearing, my sight, my bones, and my sinew are humbled to you (Allāhumma laka raka`tu wa bika āmantu wa laka aslamtu. Khasha`a laka sam`ī wa baṣarī wa `iẓāmī, wa `aṣabī).” And when he would rise he would say: “O Allah, our Lord, to You is praise filling the heaven and filling the earth, and filling what is between them, and filling whatever You have wished of things afterward (Allāhumma rabbanā lakal-ḥamdu mil’as-samāwāti wa mil’al-arḍ wa mil’a mā bainahumā, wa mil’a mā shi’ta min shay’in ba`d).” Then, when he prostrated, he would say: “O Allah, to You have I prostrated, and in You have I believed, and to You have I submitted (in Islam), my face has prostrated to the One Who created it, and fashioned it, and gave it its hearing and sight, [so] Blessed is Allah, the Best of Creators (Allāhumma laka sajadtu wa bika āmantu wa laka aslamtu, sajada wajhi lilladhī khalaqahū fa ṣuwwarahū wa shaqqa sam`ahū wa baṣarahū fatabārak Allāhu ahsanul-khāliqīn).” Then the last of what he would say between At-Tashahud and At-Taslim was: “O Allah, forgive me what I have done, before and after, and what I have hidden, and what I have done openly, and what I have transgressed the limit in, and what You know about more than me, You are the One Who sends forth and the One Who delays, there is none worthy of worship except You (Allāhummaghfirlī mā qaddamtu wa mā akhkhartu wa mā asrartu wa mā a`lantu wa mā asraftu wa mā anta a`lamu bihī minnī antal-Muqaddimu wa antal-Mu’akhkhiru, lā ilāha illā ant).”