The word(s) "four witnesses" appears 2 time(s) in 3 verse(s) in Quran in Abdullah Yusuf Ali translation.

(1) If any of your women are guilty of lewdness, Take the evidence of four (Reliable) witnesses from amongst you against them; and if they testify, confine them to houses until death do claim them, or Allah ordain for them some (other) way.

(2) And those who launch a charge against chaste women, and produce not four witnesses (to support their allegations),- flog them with eighty stripes; and reject their evidence ever after: for such men are wicked transgressors;-

(3) Why did they not bring four witnesses to prove it? When they have not brought the witnesses, such men, in the sight of Allah, (stand forth) themselves as liars!