مُسْنَدُ أَحْمَدَ
Musnad Ahmad 4166
Musnad of Abdullah bin Mas'ood
It was narrated that 'Abdullah (رضي الله عنه) said: The Messenger of Allah (ﷺ) said: "(Believing in) bird omens is shirk, (believing in) bird omens is shirk, but Allah takes away (such thoughts) by means of putting trust in Him.”
Musnad Ahmad 4194Its isnad is saheeh]