Sura al-Nisāʾ 4:103

فَإِذَا قَضَيْتُمُ ٱلصَّلَوٰةَ فَٱذْكُرُوا۟ ٱللَّـهَ قِيَٰمًا وَقُعُودًا وَعَلَىٰ جُنُوبِكُمْ فَإِذَا ٱطْمَأْنَنتُمْ فَأَقِيمُوا۟ ٱلصَّلَوٰةَ إِنَّ ٱلصَّلَوٰةَ كَانَتْ عَلَى ٱلْمُؤْمِنِينَ كِتَٰبًا مَّوْقُوتًا

fa-idhā qaḍaytumu l-ṣalāta fa-idhkurū allāha qiyāman wa-quʿūdan wa-ʿalā junūbikum fa-idhā aṭmanantum fa-aqīmū l-ṣalāta inna l-ṣalāta kānat ʿalā l-muʾminīna kitāban mawqūtan

When ye pass (Congregational) prayers, celebrate Allah's praises, standing, sitting down, or lying down on your sides; but when ye are free from danger, set up Regular Prayers: For such prayers are enjoined on believers at stated times.