The Messenger of Allah ﷺ said, "Learn the master of seeking forgiveness, 'O Allah, You are my Lord, there is no god but You. You created me and I am Your servant. I keep Your covenant and Your promise as best I can. I seek refuge in You from the evil of what I have done. I acknowledge Your favor upon me, and I acknowledge my sin, so forgive me my sin, for none forgives sins but You.'"
قال رسول الله ﷺ: تعلموا سيد الاستغفار: اللهم أنت ربي، لا إله إلا أنت، خلقتني وأنا عبدك، على عهدك ووعدك ما استطعت، وأعوذ بك من شر ما صنعت، أبوء بنعمتك علي، وأبوء بذنبي فاغفر لي ذنبي، إنه لا يغفر الذنوب إلا أنت.
Nasai narrated it in Amal al-Yawm wal-Layla (467-468), and Ibn Sunni (372), both through the route of Sari bin Yahya, from Hisham, from Abu Zubayr, from Jabir, who related it. Its chain of transmission is hasan because of Abu Zubayr, for his hadith is hasan.