Mishkat al-Masabih 9 Supplications كتاب الدعوات 170

وَعَنْ ثَوْبَانَ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «مَا مِنْ عَبْدٍ مُسْلِمٍ يَقُولُ إِذَا أَمْسَى وَإِذَا أَصْبَحَ ثَلَاثًا رَضِيتُ بِاللَّهِ رَبًّا وَبِالْإِسْلَامِ دِينًا وَبِمُحَمَّدٍ نَبِيًّا إِلَّا كَانَ حَقًّا عَلَى اللَّهِ أَنْ يُرْضِيَهُ يَوْمَ الْقِيَامَة» . رَوَاهُ أَحْمد وَالتِّرْمِذِيّ

Thauban reported God’s messenger as saying that if any Muslim says three times evening and morning, “I am pleased with God as Lord, with Islam as religion, and with Muhammad as Prophet,” God will certainly please him on the day of resurrection. Ahmad and Tirmidhi transmitted it.