مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3821
Musnad of Abdullah bin Mas'ood
It was narrated that Abdullah (رضي الله عنه) said: I heard the Messenger of Allah (ﷺ) say: "The most evil of people will be those upon whom the Hour comes when they are still alive and those who take graves as places of worship."
Musnad Ahmad 3844Its isnad is hasan]