Prayer is prescribed for believers at specified times.
فَإِذَا قَضَيۡتُمُ ٱلصَّلَوٰةَ فَٱذۡكُرُواْ ٱللَّهَ قِيَٰمࣰ ا وَقُعُودࣰ ا وَعَلَىٰ جُنُوبِكُمۡۚ فَإِذَا ٱطۡمَأۡنَنتُمۡ فَأَقِيمُواْ ٱلصَّلَوٰةَۚ إِنَّ ٱلصَّلَوٰةَ كَانَتۡ عَلَى ٱلۡمُؤۡمِنِينَ كِتَٰبࣰ ا مَّوۡقُوتࣰ ا ١٠٣
And when you have completed the prayer, remember Allah standing, sitting, or [lying] on your sides. But when you become secure, re-establish [regular] prayer. Indeed, prayer has been decreed upon the believers a decree of specified times