﴿ وَٱلْخَٰمِسَةُ أَنَّ لَعْنَتَ ٱللَّهِ عَلَيْهِ إِن كَانَ مِنَ ٱلْكَٰذِبِينَ ﴾

“and the fifth time, that God’s curse be upon him if he is telling a lie.”

and a fifth time that God’s wrath shall be upon him if he were lying in this the predicate of the subject fa-shahādatu ahadihim ‘then the testimony of one of them’ is the implicit ‘will spare him the prescribed legal punishment for false accusation’.