Abu Dawud Book 2, Hadith Number 1514.
Chapter : On seeking pardon and repentance.
Narated By Qatadah : I asked Anas: Which supplication would the Prophet (PBUH) often make? He replied: The supplication he would usually recite was: “O Allah, give us in this world what is good and in the next what is good, and protect us from the punishment of Hell-fire.”
The version of Ziyad adds: When Anas wished to supplicate, he uttered this supplication. When he uttered some other supplication, he combined it with this supplication.