2:1 heresies. The Greek term at one time referred to groups or sects in a neutral sense (cf. “sect,” Acts 24:5). It was used by Paul of divisive groups (1 Cor. 11:19; Gal. 5:20), and it came to denote the specific teachings of such groups. Here, teachings regarding Christian conduct are probably in view—conduct that placed the teachers under judgment (v. 3; 3:7).
denying the Master who bought them. Peter is not saying Christians can lose their salvation (John 10:28, 29; Rom. 8:28–30), but is describing the false teachers in terms of their own profession of faith (vv. 20, 21). By teaching and practicing immorality they despise the lordship of Christ and prove their profession to be false (1 John 2:3, 4, 19).
Though the phrase “the Master who bought them” is taken by some to mean that Christ’s substitutionary death applies to all rather than to the elect only (see “Definite Redemption” at John 10:15), Peter’s concern here is to highlight the responsibility of the false teachers rather than to advance a theory of the Atonement. With their claim to be redeemed by Christ, their “sensuality” (v. 2) brings particular dishonor on Christ and His sacrifice for sin.