Sahih Muslim Book 4, Hadith Number 1457.

Chapter : The excellence of Qunut in all the prayers when any calamity befalls the Muslims.

Qatada reported it on the authority of Anas b. Malik that the Messenger of Allah (may peace be upon him) said: When any one of you omits the prayer due to sleep or he forgets it, he should observe it when he remembers it, for Allah has said: “Observe prayer for remembrance of Me.”