“Allah does not conceal a servant (his faults) in this world except that He will conceal (them for) him on the Day of Resurrection.”

Reported by Muslim (no. 2590), from the narration of Abū Hurayrah — may Allah be pleased with him —. 

Brief Explanation of the Hadith

Allah, the Exalted, is merciful to His servants: He forgives sins and conceals faults, and He is the Most Concealing, the Most Generous. Among the signs of His vast mercy and immense forgiveness is that whoever Allah conceals in this world, not exposing him for his sin, He will also conceal him before all creation on the Day of Resurrection. Rather, He will make him acknowledge his sins in private, then He will forgive them for him. As found in Ṣaḥīḥ Muslim, from the narration of Ibn ʿUmar — may Allah be pleased with them both — in which Allah will say: “I concealed it for you in the world, and today I forgive it for you.”
This reflects the perfection of Allah’s grace: He combines for His servant both concealment and forgiveness—honoring him in this world by protecting his reputation and preserving his dignity, and in the Hereafter by concealing his sins and granting him forgiveness.
It also encourages a person to conceal his own sins if he falls into disobedience, hoping to attain this tremendous favor.
It indicates that whoever Allah conceals in this world, His generosity necessitates that He will not expose him in the Hereafter.
The hadith is a great glad tidings for those who commit sins, so long as they remain under Allah’s concealment and do not expose themselves.