From Sahih Muslim (Hadith 6840):
Qatada asked Anas which Supplication Allah's Apostle (ﷺ) frequently made. He said:The supplication that he (the Prophet made very frequently is this:" O Allah, grant us the good in this world and the good in the Hereafter and save us from the torment of Hell-Fire." He (Qatada) said that whenever Anas had to supplicate he made this very supplication, and whenever he (intended) to make another supplication he (inserted) this very supplication in that
Reference: Muslim 6840