Musannaf Ibn Abi Shaybah

Hazrat Abu Ubaidah bin Hakam Al-Azdi (may Allah have mercy on him) narrates a marfu’ hadith that the Holy Prophet Muhammad (peace and blessings be upon him) said to Hazrat Ali (may Allah be pleased with him): "Soon after me, you will strive." He (may Allah be pleased with him) asked: "O Messenger of Allah! Will this striving be for the safety of my religion?" The Prophet (peace and blessings be upon him) replied: "Yes! It will be for the protection of your religion."