The Greek verb blaptō means to harm, injure, damage, or hurt. It appears twice in the New Testament, both times in contexts describing what cannot harm those under God's protection. The word carries the sense of actual physical or spiritual damage inflicted upon a person.
Both New Testament uses of blaptō are reassuring. Mark 16:18 (in the longer ending) — handling serpents and drinking poison "will not harm them" — and Luke 4:35 — the unclean spirit threw the man down "having done him no harm." These texts together declare a profound truth: in Christ's presence and under God's protection, the enemy's power to truly harm is constrained. Paul's similar declarations (Romans 8:38–39 — nothing can separate us from God's love; Romans 8:1 — no condemnation) fill out the same theology. The harm the enemy seeks, God sovereignly limits.