كتاب صلاة المسافرين وقصرها
6  
The Book of Prayer - Travellers
(26)
Chapter: The prayer and the supplication of the Prophet (saws) at night
(26)
باب الدُّعَاءِ فِي صَلاَةِ اللَّيْلِ وَقِيَامِهِ ‏
Sahih Muslim 771 b

A'raj reported that when the Messenger of Allah (ﷺ) would start the prayer, he would pronounce takbir (Allah-o-Akbar) and then say:

I turn my face (up to Thee), I am the first of the believers; and when he raised his head from ruku' he said: Allah listened to him who praised Him; O our Lord, praise be to Thee; and he said: He shaped (man) and how fine is his shape? And he (the narrator) said: When he pronounced salutation he said: O Allah, forgive me my earlier (sins), to the end of the hadith; and he did not say it between the Tashahhud and salutation (as mentioned above).
وَحَدَّثَنَاهُ زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ مَهْدِيٍّ، ح وَحَدَّثَنَا إِسْحَاقُ بْنُ، إِبْرَاهِيمَ أَخْبَرَنَا أَبُو النَّضْرِ، قَالَ حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ عَبْدِ اللَّهِ بْنِ أَبِي سَلَمَةَ، عَنْ عَمِّهِ، الْمَاجِشُونِ بْنِ أَبِي سَلَمَةَ عَنِ الأَعْرَجِ، بِهَذَا الإِسْنَادِ وَقَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا اسْتَفْتَحَ الصَّلاَةَ كَبَّرَ ثُمَّ قَالَ ‏"‏ وَجَّهْتُ وَجْهِي ‏"‏ ‏.‏ وَقَالَ ‏"‏ وَأَنَا أَوَّلُ الْمُسْلِمِينَ ‏"‏ ‏.‏ وَقَالَ وَإِذَا رَفَعَ رَأْسَهُ مِنَ الرُّكُوعِ قَالَ ‏"‏ سَمِعَ اللَّهُ لِمَنْ حَمِدَهُ رَبَّنَا وَلَكَ الْحَمْدُ ‏"‏ ‏.‏ وَقَالَ ‏"‏ وَصَوَّرَهُ فَأَحْسَنَ صُوَرَهُ ‏"‏ ‏.‏ وَقَالَ وَإِذَا سَلَّمَ قَالَ ‏"‏ اللَّهُمَّ اغْفِرْ لِي مَا قَدَّمْتُ ‏"‏ .‏ إِلَى آخِرِ الْحَدِيثِ وَلَمْ يَقُلْ بَيْنَ التَّشَهُّدِ وَالتَّسْلِيمِ ‏.‏
Reference : Sahih Muslim 771b
In-book reference : Book 6, Hadith 241
USC-MSA web (English) reference : Book 4, Hadith 1696
  (deprecated numbering scheme)