With the metaphor of building, Jude is using language that is also found elsewhere in the New Testament (for example, Romans 15:2, Romans 15:20; 1 Thessalonians 5:11; Ephesians 2:21; Ephesians 4:12, Ephesians 4:16, Ephesians 4:29; Acts 9:31; 1 Peter 2:5, 1 Peter 2:7). He is calling on the church to labour together for corporate growth, growth to which every member must contribute (1 Peter 4:10–11). The Greek word which he uses signifies building on foundations that have already been laid, which is the faith that they received from the apostles. They must not depart from this foundation.
20 But you, beloved, building yourselves up in your most holy faith and praying in the Holy Spirit,