Former Lusts (14): Peter works out the implications of our great salvation in Christ by first fixing our hope on future grace (1:13). Then, he directs us to our duties for the present life. As he begins this second imperative, Peter reminds us who we are in Christ, viz., obedient children. By the great mercy of God, He has regenerated[1] us to be “obedient children.”[2] As such, we are no longer to conform ourselves[3] to the former lusts—the strong and sinful desires that stemmed from biblical ignorance. We were once like orphaned children without standards and without training, but now we belong to the family of God and we know His truth and His standards. Thus, as well-taught children, we maintain a healthy distance from the former and foolish lusts of ignorance.

Present Holiness (15-16): As the cup is washed so it can receive fresh water, so we are cleansed from sin so that we may be filled with the holiness of our God (“the Holy One”), where His truth (contra “ignorance”) and character permeate every facet of life (“in all your behavior”). Peter gives this command with authority because of Scripture (“because it is written”). God’s purpose for His people is unchanged between the testaments.[4] And we, as His people,[5] are to reflect the luminance of His holiness. As the moon waxes brightly the light of the sun, so we evermore reflect the radiant glory of our holy God.

[1] We are new creatures in Christ (2 Cor. 5:17) through regeneration (1:3; John 1:12-13; 3:3). We exist for the Lord and His glory (Rom. 14:8; 1 Cor. 10:31). We have embraced the new life “created in righteousness and holiness of the truth” (Eph. 4:24) and abandoned the old life (Mark 8:34-35; Rom. 6:4; Gal. 2:20; 5:24; 6:14).

[2] Cf. 1:2, 22. True saving faith is marked by obedience and unbelief by disobedience: Matt. 28:20; John 3:36; Acts 5:32; Rom. 6:17; Eph. 2:2; 5:6; Col. 3:6; Heb. 4:6, 11; 5:9; 1 Pet. 2:8.

[3] The verb for “do not be conformed” is in the middle voice, emphasizing our active participation in this.

[4] God’s purpose for His people has always been redemption from sin unto faith and obedience to Him through a new and circumcised heart. Cf. Deut. 5:29; 10:16; 29:4; 30:6; Ezek. 11:19-20; 36:25-27; Rom. 2:5, 29.

[5] This is precisely 2:9-10, that we are God’s people, even though we have not replaced Israel (Rom. 11:23-25).