But ye, beloved ,.... See Gill on 1:17 ,

building up yourselves on your most holy faith ; some copies, and the Complutensian edition, read, "our most holy faith"; meaning the doctrine of faith in all its branches, which is holy, a most holy doctrine; which displays the holiness of God, and is a means of beginning and increasing internal holiness in the saints, and of encouraging and exciting them to external holiness of life and conversation: this phrase, מהימנותא קדישא , "holy faith", is in use with the Jews F11 Zohar in Gen. fol. 47. 4. : and it becomes the saints to build up one another upon this; the doctrine of faith, is a foundation to build upon, particularly what regards the person, offices, and grace of Christ, and is itself of an edifying nature; and they should not content themselves with their present knowledge of it, but seek for an improvement in it; and though they were passive when first built on Christ and his doctrines, and though ministers are greatly instruments in building of them up more and more; yet they are capable of building up themselves, and one another, by attending on the ministry of the word, and by private conversation, with each other, and particularly by

praying in the Holy Ghost ; which is a special means of increase and establishment in the doctrine of faith; the Holy Ghost is the author and enditer of prayer, and an assister in it; without him saints cannot call God their Father, nor pray with faith and fervency, or with freedom and liberty,