Quran 24:13 — Light (Al-Noor)

لَولا جاءو عَلَيهِ بِأَربَعَةِ شُهَداءَ ۚ فَإِذ لَم يَأتوا بِالشُّهَداءِ فَأُولٰئِكَ عِندَ اللَّهِ هُمُ الكٰذِبونَ

Only if they produced four witnesses (you may believe them). If they fail to produce the witnesses, then they are, according to GOD, liars.

[24:12] When you heard it, the believing men and the believing women should have had better thoughts about themselves, and should have said, "This is obviously a big lie."

[24:14] If it were not for GOD's grace towards you, and His mercy in this world and in the Hereafter, you would have suffered a great retribution because of this incident.