The Messenger of Allah (ﷺ), used to prostrate and say:

اَللَّهُمَّ لَكَ سَجَدْتُ وَلَكَ أَسْلَمْتُ، وَبِكَ آمَنْتُ، سَجَدَ وَجْهِيَ لِلَّذِي خَلَقَهُ، وَصَوَّرَهُ، فَأَحْسَنَ صُوْرَتَهُ وَشَقَّ سَمْعَهُ وَبَصَرَهُ، تَبَارَكَ اللَّهُ أَحْسَنُ الْخَالِقِينَ

Allaahumma laka sajadtu wa laka 'aslamtu, wa bika 'aamantu sajada wajhiya lilladhee khalaqahu, wa sawwarahu fa'ahsana su-ratahu, wa shaqqa sam'ahu wa basarahu, tabaarakAllahu 'ahsanul-khaaliqeen

O Allah, to You I prostrate myselfm, to You I have submitted, and in You I believe. My face is prostrated to the One Who created it, fashioned it, and gave it hearing and sight. Blessed is Allah, the Best of creators.

Reference: Sahih (Albani). Nasai: 1126