The Prophet ﷺ, in a long hadith, reported that when he bowed in ruku he would say, "O Allah, to You I have bowed, in You I have believed, and to You I have submitted. My hearing, my sight, my mind, my bones, and my sinews are humbled before You."When he rose from ruku he would say, "O Allah, our Lord, to You belongs all praise, filling the heavens, filling the earth, filling what lies between them, and filling whatever else You will."
عن النبي ﷺ في حديث طويل: وإذا ركع قال: اللهم لك ركعت، وبك آمنت، ولك أسلمت، خشع لك سمعي وبصري، ومخي وعظمي وعصبي. وإذا رفع قال: اللهم ربنا لك الحمد ملا السماوات وملأ الأرض وملا ما بينهما، وملا ما شئت من شيء بعد.
Muslim reported it in "The Prayer of Travelers" (771:201), from Muhammad bin Abu Bakr Muqaddami, who said, Yusuf Majishun narrated to us, who said, My father narrated to me, from Abdul-Rahman Araj, from Ubaydullah bin Abu Rafi, from Ali bin Abu Talib, and he related it.