مُسْنَدُ أَحْمَدَ
Musnad Ahmad 4042
Musnad of Abdullah bin Mas'ood
It was narrated that ‘Abdullah said: We were with The Messenger of Allah (ﷺ) in the cave and a snake appeared. We rushed to kill it but it got away from us and entered the hole. The Prophet (ﷺ) said: "It was protected from your evil as you were protected from its evil.”
Musnad Ahmad 4068Its isnad is saheeh, al-Bukhari (3317) and Muslim (2234)]