مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3747
Musnad of Abdullah bin Mas'ood
It was narrated that 'Abdullah bin Mas'ood (رضي الله عنه) said: The Messenger of Allah (ﷺ) liked to repeat supplications three times, and prayers for forgiveness three times.
Musnad Ahmad 3770This hadeeth is not repeated in this place in any of the man