Surah An-Nur, Verse 2

ٱلزَّانِيَةُ وَٱلزَّانِي فَٱجۡلِدُواْ كُلَّ وَٰحِدٖ مِّنۡهُمَا مِاْئَةَ جَلۡدَةٖۖ وَلَا تَأۡخُذۡكُم بِهِمَا رَأۡفَةٞ فِي دِينِ ٱللَّهِ إِن كُنتُمۡ تُؤۡمِنُونَ بِٱللَّهِ وَٱلۡيَوۡمِ ٱلۡأٓخِرِۖ وَلۡيَشۡهَدۡ عَذَابَهُمَا طَآئِفَةٞ مِّنَ ٱلۡمُؤۡمِنِينَ٢

al-zāniyatu wal-zānī fa-ij'lidū kulla wāḥidin min'humā mi-ata jaldatin walā takhudh'kum bihimā rafatun fī dīni l-lahi in kuntum tu'minūna bil-lahi wal-yawmi l-ākhiri walyashhad ʿadhābahumā ṭāifatun mina l-mu'minīna

The [unmarried] woman or [unmarried] man found guilty of sexual intercourse - lash each one of them with a hundred lashes, and do not be taken by pity for them in the religion [i.e., law] of Allāh, if you should believe in Allāh and the Last Day. And let a group of the believers witness their punishment.