Sahih al-Bukhari, Volume 8, Book 75, Hadith 398 (USC-MSA) ⓘ
Narrated Anas: The most frequent invocation of The Prophet was: "O Allah! Give to us in the world that which is good and in the Hereafter that which is good, and save us from the torment of the Fire." (2.201)
حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا عَبْدُ الْوَارِثِ، عَنْ عَبْدِ الْعَزِيزِ، عَنْ أَنَسٍ، قَالَ كَانَ أَكْثَرُ دُعَاءِ النَّبِيِّ صلى الله عليه وسلم " اللَّهُمَّ رَبَّنَا آتِنَا فِي الدُّنْيَا حَسَنَةً، وَفِي الآخِرَةِ حَسَنَةً، وَقِنَا عَذَابَ النَّارِ " .
also referenced under: Book 80, Hadith 84 (In-Book) & Hadith 6389 (DarusSalam)