Ibn Abbas (may Allah be pleased with them both) said: "Why did they not bring four witnesses to it?" — had they done so, they and those who testified would all have been deemed liars — "And since they did not bring the witnesses, it is they who are the liars in the sight of Allah" [Surah An-Nur: 13], meaning sheer lying.
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 19494