The Messenger of Allah ﷺ used to like to repeat his supplication three times and to seek forgiveness three times.
حدثنا أحمد بن علي بن سويد السدوسي حدثنا أبو داود عن إسرائيل عن أبي إسحق عن عمرو بن ميمون
أن رسول الله ﷺ كان يعجبه أن يدعو ثلاثا ويستغفر ثلاثا
[Its chain is daif] Nasai reported it in Al-Kubra, no. 10291, and Ahmad, 1/394, 397, from the hadith of Israil, through this route, and Ibn Hibban graded it sahih, no. 2410.* Abu Ishaq is a mudallis and he narrated it using "an" (indicating possible concealment of the chain).