مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2946
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from Ibn 'Abbas (رضي الله عنه) that The Prophet (ﷺ) said: "Every Muslim must do Hajj, and if I were to say every year, it would be (obligatory)."
Musnad Ahmad 2969A Saheeh hadeeth; this is a da'eef isnad]