By the words "most holy faith," we may understand chiefly the grand truths of the everlasting gospel which are revealed unto and embraced by faith. And they are called "our most holy faith," because they are imbued with all the holiness of God; and not only so, but as they are received into believing hearts, communicate sanctification, because they have a liberating, sanctifying efficacy.
The words "build up" assume that there is a foundation laid. Christ is that foundation which God hath laid in Zion, a chief corner-stone, elect, precious; and where Christ is revealed to the soul by a divine power, a foundation is laid in the heart on which every subsequent truth is to be built up. The grand thing to be clear of in our own experience is, whether Christ has been laid as a foundation in our souls or not, and if he has, we have been driven from every other as finding no rest or peace but in him. If ever he has been revealed to our souls by the mighty power of God, then we have seen and felt that in him there is a foundation on which we can stand, and that for eternity.
As the Son of the Father in truth and love; having come to finish the work which the Father gave him to do; having put away sin by the sacrifice of himself, and brought in an everlasting righteousness in which we may stand justified, there is a foundation on which a poor, guilty soul may rest. When this foundation is brought nigh, and we, by the power of God's grace, are lifted up to rest upon it, we can say,
"How firm a foundation, ye saints of the Lord,
Is laid for your faith in his excellent word."
"Other foundation can no man lay than that is laid, which is Jesus Christ" (1 Cor. 3:11).