Musnad Ahmad 988:2

Hajjaj narrated to us, Laith narrated to us, Yazid ibn Abi Habib narrated to me, from Rabi'ah ibn Laqit al-Tujibi, from Abdullah ibn Hawalah al-Azdi, from the Messenger of Allah (peace and blessings of Allah be upon him) that he said: "Whoever is saved from three things has indeed been saved." He said it three times. They said: "What are they, O Messenger of Allah?" He said: "My death, the killing of a caliph who is patient and adheres to the truth, and the Dajjal."