New Defender's Study Bible Notes
3:2 shall be like him. We have been predestined “to be conformed to the image of His Son” (Romans 8:29), because when He comes again, He “shall change our vile body, that it may be fashioned like unto His glorious body” (Philippians 3:21). He will “make all things new” again (Revelation 21:5). Although the Bible does not say specifically, perhaps this means that those who died in old age will be made young again, and those who died in infancy will grow to vigorous maturity, so that all who are Christ’s “shall be like Him.”
3:3 purifieth himself. The hope of Christ’s second coming is not a dead hope, but a “lively hope” (I Peter 1:3); not a frightening prospect, but a “blessed hope” (Titus 2:13). It is a joyful hope (I Thessalonians 2:19), a comforting hope (I Thessalonians 4:13-18), a hope of glory (Colossians 1:27) and an anchoring hope (Hebrews 6:19). Finally, as this verse notes, it is a purifying hope, for it stimulates us to abide in Him.