Jude 1:20

But ye, beloved. As in the literal translation of v. 17 (see comment there), with the present emphasis on the true believer as distinct from the self-seeking disrupter of churches.

Building up. Jude admonishes his readers to build up their faith as a defense against the deceivers, who have been so active in breaking down their own spiritual life and that of others. For the figure of “building up” see on Acts 9:31; 20:32; cf. on 1 Peter 2:5.

On your most holy faith. Or, “by your most holy faith,” that is, the Christian faith, all that the church teaches concerning Christ. Paul speaks of building upon the foundation of the apostles, prophets, and Jesus Christ (Eph. 2:20), and it is probable that Jude has a similar thought in mind. The readers’ personal faith in Jesus Christ would hardly be described as “most holy.”

Praying in the Holy Ghost. That is, praying in accordance with the Holy Spirit’s directives and with the Spirit’s aid (cf. on Acts 9:31; Eph. 6:18). For comment on the spiritual value of prayer see on Luke 18:1.