مُسْنَدُ أَحْمَدَ
Musnad Ahmad 4165
Musnad of Abdullah bin Mas'ood
It was narrated that ‘Abdullah said: The Messenger of Allah (ﷺ) said: “Whoever sees me in a dream has indeed seen me, for verily the Shaitan cannot appear in my form."
Musnad Ahmad 4193lts isnad is saheeh]