The supplications of the Prophet Muhammad ﷺ

"The best way of seeking forgiveness is to say: 'O Allah, You are my Lord; there is no god but You. You created me and I am Your servant, and I keep to Your covenant and Your promise as far as I can. I seek refuge in You from the evil of what I have done. I acknowledge before You Your favour upon me, and I acknowledge my sin, so forgive me, for none forgives sins but You.' Whoever says it during the day with certainty and dies that day before evening will be among the people of Paradise; and whoever says it at night with certainty and dies before morning will be among the people of Paradise."