مُسْنَدُ أَحْمَدَ
Musnad Ahmad 4302
Musnad of Abdullah bin Mas'ood
It was narrated from Ibn Mas’ood that The Messenger of Allah (ﷺ) said: "I will reach the Cistern ahead of you, and I will plead for some people of my ummah, but I will have to give them up. I will say: 'O Lord, my companions, my companions.' But it will be said: ‘You do not know what they did after you were gone."
Musnad Ahmad 4332Saheeh, its isnad is hasan]