Noah Webster's Dictionary (a.) Committing no mistake; incapable or error or failure certain; sure; unfailing; as, the unerring wisdom of God.

Multi-Version Concordance Unerring (1 Occurrence) Acts 28:4 When the natives saw the creature hanging to his hand, they said to one another, "Beyond doubt this man is a murderer, for, though saved from the sea, unerring Justice does not permit him to live." (WEY)