The Greek verb apodidōmi (from apo 'back' + didōmi 'to give') means to give back what is owed — to pay a debt, fulfill a duty, render what belongs to another, or recompense. It is one of the most theologically loaded 'giving' verbs in the New Testament.
Apodidōmi carries the weight of accountability and the promise of divine justice. 'Render to Caesar what is Caesar's and to God what is God's' (Matthew 22:21) — both imperatives use apodidōmi, placing civic obligation and total self-surrender to God in the same grammatical frame. In Romans 12:17 and 1 Thessalonians 5:15, believers are commanded not to repay (apodidōmi) evil for evil — breaking the revenge cycle. But God himself will apodidōmi every person according to their works (Matthew 16:27; Romans 2:6; Revelation 22:12). This word is the grammar of divine justice: every debt will be settled, every service rewarded, every evil ultimately repaid — by God, not us.