Explanation

The Prophet (may Allah's peace and blessings be upon him) used to say at the end of prayer, between the Tashahhud and Taslīm: "O Allah, Forgive my past and future sins, my secret and open sins, my transgression." He went to great lengths in asking his Lord for forgiveness by mentioning various types of sins. "And that of which You have better knowledge than I", meaning: my sins whose number and gravity are unknown to me. "Indeed, You are the One Who puts forward", meaning: you bring some slaves close to You by enabling them to obey and worship You. "And You are the One Who puts back", meaning: You make some of them lag behind through failure to act in a way pleasing to You. Or You put whomever You will at the ranks of perfection and keep whomever You will away from high ranks and deep into the lowest ones. "There is no god but You." There is no one worthy of being worshiped except You.