Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: "The prayers are the good deeds. The expiation for what is between the Zuhr prayer and Asr is the Asr prayer; the expiation for what is between Asr and Maghrib is the Maghrib prayer; the expiation for what is between Maghrib and Isha is the Isha prayer. Then the Muslim retires to his bed with no sin upon him, as long as he has avoided the major sins." Then he recited this verse: "Indeed, good deeds wipe away evil deeds" [Surah Hud: 114].
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8706