The Christian is to strive for the standard of purity that Christ attained (cf. on Phil. 3:8-15). He gained the victory over every besetment (see on John 8:46; 2 Cor. 5:21; 1 Peter 2:22), and made it possible for all men to live similarly victorious lives (see on Matt. 1:21; Rom. 7:24, 25; 8:1, 2; 1 John 1:9).

 Gr. hagnizō, “to cleanse from defilement,” “to purify.” The word is applied to both ceremonial and moral cleansing (John 11:55; Acts 21:24, 26; 24:18; James 4:8; 1 Peter 1:22). Sinful man cannot cleanse himself; he is sold under sin and utterly dependent upon the Saviour for purity (Jer. 17:9; John 3:3; 15:4, 5; Rom. 8:7). Nevertheless, there is some work that man, with divine aid, must do for himself (see on Phil. 2:12, 13). This work demands diligent watching and prayer (Eph. 6:13-18; Col. 4:2; Rev. 3:3). The central struggle is to maintain faith in the victory that Christ has gained for us, and to live believing that His grace is sufficient to give us the mastery over every besetment (Gal. 2:20; Phil. 4:13; SC 47, 48; MH 159). By his statement concerning purification John refutes the Gnostic claim that the Christian hope could be held without reference to one’s morality. All who genuinely long to see Christ will strive for purity of life.

Or, “upon him,” that is, on Christ. John is writing of the hope that is centered on Jesus, and is not primarily thinking of the hope as existing in the one who hopes.

The writer refers, not to those who vaguely hope for the Saviour’s appearing, but to the believer who firmly holds to a clearly defined expectation of Christ’s return.