ثُمَّ يُجْزَىٰهُ ٱلْجَزَآءَ ٱلْأَوْفَىٰ
Summa yujzaahul jazaaa 'al awfaa
and then be repaid for it in full,
Awfa is the elative form of wafa, to pay in full, the language of weights and measures where a debt is discharged to the last portion. Wafa also opened this passage a few verses back, describing Ibrahim as the one who fulfilled what was asked of him; what a person renders there returns here as what is rendered to him. The construction doubles the verb with its own noun.