Musnad Ahmad 4016

It was narrated that ‘Abdullah (رضي الله عنه) said: The Messenger of Allah (ﷺ) said: “I will reach the Cistern ahead of you, and I will pead concerning some people then I will have to give them up. I will say: ‘O Lord, my companions!’ It will be said:[g] ‘You do not know what they did after you were gone.’”