مُسْنَدُ أَحْمَدَ
Musnad Ahmad 2194
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated from from Ibn 'Abbas (رضي الله عنه) that The Prophet (ﷺ) married Maimoonah bint al-Harith when they were both in ihram.
Musnad Ahmad 2200lts isnad is saheeh]