Quran 24:6 — Light (Al-Noor)

As for those who accuse their own spouses, without any other witnesses, then the testimony may be accepted if he swears by GOD four times that he is telling the truth.

[24:5] If they repent afterwards and reform, then GOD is Forgiver, Merciful.

[24:7] The fifth oath shall be to incur GOD's condemnation upon him, if he was lying.