Surah al-Nur is Medinan (1).
In the Name of Allah, the Most Compassionate, the Most Merciful.
“A surah which We have sent down and made obligatory, and in which We have sent down clear verses, so that you may take heed. As for the adulteress and the adulterer, flog each of them with one hundred lashes. Let no pity for them prevent you from carrying out Allah’s religion, if you truly believe in Allah and the Last Day; and let a group of the believers witness their punishment.” (1–2)
“A surah”—that is, this is a surah—“which We have sent down and made obligatory.” Ibn Kathir and Abu ‘Amr recited it with the letter r doubled: “and We have made its obligations numerous,” whereas the others recited it without doubling. That is, We have made obligatory the rulings contained in it and required you to act upon them.
It is also said that it means: We have determined the prescribed punishments contained in it, for farḍ means determination. Allah, exalted is He, says: “Then half of what you have stipulated” (al-Baqarah 2:237), meaning, what you have determined. Evidence for the undoubled reading is His saying, exalted is He: “Indeed, He who has imposed the Quran upon you...” (al-Qasas 28:85).
As for the doubled reading, it means: ⦗34/A⦘ We have expounded it in detail and made it clear. It is also said that it bears the same meaning as farḍ in the sense of obligation; the doubling indicates abundance because of the many obligations it contains. That is, We have made it obligatory upon you and upon those after you until the Hour is established.
“And in which We have sent down clear verses”: that is, plain and evident verses. “So that you may take heed”: that is, so that you may be admonished.
His saying, exalted is He, “As for the adulteress and the adulterer, flog each of them with one hundred lashes,” refers to when they are free, adult, sane, unmarried persons who have never been married, and are not muhsan. “Flog”: that is, strike each of them with one hundred lashes. One says, “He flogged him,” when he struck his skin, just as one says that he struck him on the head or on the stomach when he strikes his head or stomach. It is expressed in terms of the skin so that the beating is not excessive and he is not struck