The Hebrew verb naqah (נָקָה) means to be clean, innocent, free from guilt, or to go unpunished. It appears about 44 times in the OT. Its adjective form is naqi (innocent, clean).
Naqah is a judicial term — it speaks to legal standing before God and men. Crucially, God declares He will by no means leave the guilty unpunished (Exodus 34:7), showing that sin demands consequence. This is the problem of the human condition. Yet the gospel answers naqah: through the atoning death of Christ, who bore guilt so that we might be declared naqi — clean, innocent, free. The Psalmist pleads for naqah: 'Cleanse me from hidden faults' (Psalm 19:12). This is the heart of justification — God clearing the guilty through the cross.