Musnad Ahmad 26:630

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Mughirah, who said: I heard Abu Wa'il narrating from Abdullah, from the Prophet, may Allah bless him and grant him peace, that he said: "I am your forerunner at the Hawd (the Cistern). Men from among you will be raised to me, then they will be snatched away from before me. I will say: 'O Lord, my companions!' It will be said to me: 'Indeed, you do not know what they innovated after you.'"