Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: "You keep burning (with sins) until, when you pray Fajr, it is washed away; then you keep burning until, when you pray Zuhr, it is washed away; then you keep burning until, when you pray Asr, it is washed away," until he mentioned all the prayers in this way.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8707