The Greek verb hagnizo (ἁγνίζω) means to purify, to cleanse ritually or morally, or to sanctify. It appears 7 times in the New Testament and covers both the ceremonial purification practices of Judaism (Acts 21:24-26; John 11:55) and the moral/spiritual self-purification called for in the epistles.
The word is related to hagnos (G53, pure, chaste) and carries the sense of making something or someone ritually or morally fit to stand in the presence of holiness. It is the verbal action of bringing about purity.
Hagnizo bridges the old covenant's ritual purity system and the new covenant's call to moral and spiritual purity. In John 11:55, Jews purifying themselves before Passover perform hagnizo — the traditional ceremonial washing. In Acts 21, Paul himself undergoes ritual purification to demonstrate his respect for Jewish custom. Yet in the epistles, the word takes on its deeper moral and eschatological significance.
The most theologically rich use of hagnizo is in 1 John 3:3: "All who have this hope in him purify themselves, just as he is pure." Christian purification is not a return to ritual washing but an ongoing moral and spiritual process — motivated by the hope of Christ's return and modeled on Christ's own purity. The eschatological vision (seeing Christ as He is) produces present transformation. Hope purifies.