The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 1217
Abu Huraira reported: The Messenger of Allah (way peace be upon him) said: When any one of you utters tashahhud (in prayer) he must seek refuge with Allah from four (trials) and should thus say:" O Allah! I seek refuge with Thee from the torment of the Hell, from the torment of the grave, from the trial of life and death and from the evil of the trial of Masih al-Dajjal" (Antichrist).