The Hebrew adjective naqiy means innocent, clean, or free from guilt and penalty. Used about 43 times in the OT, it describes someone who is legally guiltless before a court or morally pure before God. It can also mean exempt from obligation or punishment.
Naqiy sets the standard for divine justice: God will not acquit the guilty (lo yenaqeh) or condemn the innocent. The prohibition against shedding innocent (naqiy) blood is a repeated moral imperative in the OT. Christ, the perfectly innocent One, shed His blood in place of the guilty — making the guilty naqiy before God. This word underlies the doctrine of justification: being declared clean before God.