Sahih Muslim 590
The Book of Mosques and Places of Prayer
From what refuge is to be sought when in salat
Ibn 'Abbas reported that the Messenger of Allah (ﷺ) used to teach them this supplication (in the same spirit) with which he used to teach them a surah of the Qur'an. He would thus instruct us: "Say, O Allah, we seek refuge with You from the torment of Hell. And I seek refuge with You from the torment of the grave, and I seek refuge with You from the trial of al-Masih ad-Dajjal, and I seek refuge with You from the trial of life and death." Muslim b. Hajjaj said: It has reached me that Tawus said to his son: Did you make this supplication in prayer? He said: No. (Upon this) he (Tawus) said: Repeat the prayer. Tawus has narrated this hadith through three or four (transmitters) with words to the same effect.