The Prophet ﷺ used to say when prostrating: "Allahumma laka sajadtu wa laka aslamtu wa anta Rabbi, sajada wajhi lilladhi khalaqahu wa sawwarahu wa shaqqa sam'ahu wa basarahu, tabarak Allahu ahsanul-khaliqin ( O Allah, to You I have prostrated and in You I have believed and to You I have submitted, and You are my Lord. My face has prostrated to the One Who created it and formed it, and brought forth its hearing and sight. Blessed be Allah the best of Creators.)"  

عَنِ النَّبِيِّ ﷺ كَانَ يَقُولُ فِي سُجُودِهِ اللَّهُمَّ لَكَ سَجَدْتُ وَبِكَ آمَنْتُ وَلَكَ أَسْلَمْتُ وَأَنْتَ رَبِّي سَجَدَ وَجْهِي لِلَّذِي خَلَقَهُ وَصَوَّرَهُ وَشَقَّ سَمْعَهُ وَبَصَرَهُ تَبَارَكَ اللَّهُ أَحْسَنُ الْخَالِقِينَ