Maliks Muwatta Book 15, Hadith Number 33.

Yahya related to me from Malik from Abu’zZubayr al-Makki from Tawus al-Yamani from Abdullah ibn Abbas that the Messenger of Allah, may Allah bless him and grant him peace, used to teach this dua in the same way that he would teach them a sura of the Qur’an, “O Allah, I seek refuge in You from the torment of Jahannam, and I seek refuge in You from the trial of the Dajjal, and I seek refuge in You from the trial of life and death.”

Allahumma inniy audhu bika min adhabi jahannama, wa audhu bika min adhabi’l-qabri, wa audhu bika min fitnati’l-mahya wa mamati.