Ibn Mas’ud reported: The Messenger of Allah, peace and blessings be upon him, when he would supplicate, he would supplicate three times, and when he would ask Allah, he would ask three times.
Source: Ṣaḥīḥ Muslim 1794
Grade: Sahih (authentic) according to Muslim
عَنْ ابْنِ مَسْعُودٍ قَالَ كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا دَعَا دَعَا ثَلَاثًا وَإِذَا سَأَلَ اللَّه سَأَلَ ثَلَاثًا
1794 صحيح مسلم كتاب الجهاد والسير باب ما لقي النبي صلى الله عليه وسلم من أذى المشركين والمنافقين