مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3811
Musnad of Abdullah bin Mas'ood
It was narrated that 'Abdullah (رضي الله عنه) said: The Messenger of Allah (ﷺ) said: “I give you permission to raise the curtain."
Musnad Ahmad 3834A saheeh hadeeth. This is a da'eef isnad because of ambiguit