Whenever anyone accepted Islam, the Prophet (ﷺ) used to teach him how to pray then he would instruct...
Reference:Muslim 4/2073, and in one of Muslim's reports there is the addition: 'For these words combine [the goodness of] this world and the next.'Hisnul Muslim 263
كَانَ الرَّجُلُ إِذَا أَسْلَمَ عَلَّمَهُ النَّبيُّ صلى الله عليه وسلم الصَّلاَةَ ثُمَّ أَمَرَهُ أَنْ يَدْعُوَ بِهَؤُلاَءِ الْكَلِمَاتِ: (اللَّهُمَّ اغْفِرِ لِي وَارْحَمْنِي وَاهْدِنِي وَعَافِنِي وَارْزُقْنِي)
Allāhummaghfir lī, warḥamnī, waḥdinī, wa `āfinī warzuqnī
Whenever anyone accepted Islam, the Prophet (ﷺ) used to teach him how to pray then he would instruct him to invoke Allah with the following words: O Allah forgive me, and have mercy on me and guide me and give me good health and provide for me.