But ye, beloved, building up yourselves on your most holy faith - Compare the notes at Jude 1:3. On the word “building,” see the 1 Corinthians 3:9-10 notes; Ephesians 2:20 note. It is said here that they were to “build up themselves;” that is, they were to act as moral and responsible agents in this, or were to put forth their own proper exertions to do it. Dependent, as we are, and as all persons with correct views will feel themselves to be, yet it is proper to endeavor to do the work of religion as if we had ample power of ourselves. See the notes at Philippians 2:12. The phrase “most holy faith” here refers to the system of religion which was founded on faith; and the meaning is, that they should seek to establish themselves most firmly in the belief of the doctrines, and in the practice of the duties of that system of religion.
Praying in the Holy Ghost - See the notes at Ephesians 6:18.