But ye, beloved, building up yourselves on your most holy faith, praying in the Holy Ghost,
Resuming Jude 1:17.
Building up yourselves - opposite to "separate themselves" (Jude 1:19); as "in the Holy Spirit" is opposed to "having not the Spirit."
On - as on a foundation. Building on THE FAITH is building on Christ, its object.
Praying in the Holy Spirit - (Romans 8:26.) The Holy Spirit teaches what we are to pray for, and how. None can pray aright except by being in the Spirit - i:e., in the elements of His influence. Chrysostom mentions among the Spirit's gifts at the beginning of the New Testament, that of prayer, bestowed on some, who prayed in the name of the rest, and taught others to pray. Their prayers so conceived, and often used, were preserved among Christians; and out of them forms were framed. Such is the origin of liturgies (Hammond).