مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3503
Musnad of 'Abdullah bin al-'Abbas bin 'Abdul-Muttalib from the Prophet
It was narrated that al-Muttalib bin ‘Abdullah said: Ibn 'Umar used to do wudoo' washing each part three times, and he attributed that to the Prophet (ﷺ). And Ibn ‘Abbas (رضي الله عنه) used to do wudoo' washing each part once, and he attributed that to the Prophet (ﷺ).
Musnad Ahmad 3526Saheeh because of corroborating evidence]