﴿ فَإِن تَوَلَّوْا۟ فَإِنَّ ٱللَّهَ عَلِيمٌۢ بِٱلْمُفْسِدِينَ ﴾

“And if they turn away [from this truth] - behold, God has full knowledge of the spreaders of corruption.”

(And if they turn away) from joining the Prophet (pbuh) in invoking Allah's curse on those who lie about Him regarding Jesus (then Lo! Allah is Aware of (who are) the corrupters) i.e. the Christians of Najran.