Whenever the Messenger of Allah ﷺ finished his prayer, he would seek forgiveness from Allah three times and say, "O Allah, You are Peace, and from You comes peace. Blessed are You, Possessor of Majesty and Honor."Walid said, "I asked Awzai, 'How is the seeking of forgiveness done?'"He replied, "You say, 'I seek forgiveness from Allah, I seek forgiveness from Allah.'"
كان رسول الله ﷺ إذا انصرف من صلاته، استغفر الله ثلاثا وقال: اللهم أنت السلام، ومنك السلام، تباركت ذا الجلال والإكرام. قال الوليد: فقلت للأوزاعي: كيف الاستغفار؟ قال: تقول: أستغفر الله، أستغفر الله.
Muslim reported it in Chapters on Mosques (591) from Dawud bin Rashid, who said, Walid narrated to us, from Uzai, from Abu Ammar (whose name was Shaddad bin Abdullah), from Abu Asma, from Thawban, who mentioned it.