1 Samuel 14:35

Saul built an altar to the Lord. He built an altar to offer a holocaust upon it and to intervene for the sin of the people, which they had rashly committed. Every perfect teacher builds in the hearts of the hearers the faith in the Lord's Passion, where on the altar of the living cross that precious blood was shed for the remission of sins, clearly instructing all by this example; for if the end of the Lord was death, much more should the servants mortify their members which are on earth; fornication, uncleanness, lust, evil desire, and covetousness, which is idolatry (Colossians III), and such things that are works of the flesh and blood, clearly cannot be associated with the fruit of the Spirit. But also, daily revisiting the sayings or acts of the old fathers and the people, and desiring through these to be spiritually refreshed while struggling against enemies, as many of us who perceive only according to the letter of such great authority we feel, as if killing oxen and sheep on the earth, we eat with the blood; because handling heavenly matters with a carnal and earthly eye. But whoever recognizes that all things are spiritually summed up in Christ and the Church, upon that great rock, which was cut from the mountain without hands and grew, destroying the empire of the world, and filled the whole earth, we kill without harm and feast, constructing an altar of our devotion and pious sense pleasing to the Lord.

For when sinners are converted, a heavenly edifice is, as it were, constructed from stones. And since many manuscripts have: "And then Saul first began to build," the name of altar can be understood as compunction of heart. For when compunction of heart is raised up through the word of a teacher, an altar is surely built to the Lord. And it is said to have been built first, because there is a compunction of love. Hence in the tabernacle of the covenant, two altars were commanded by the Lord to be made: one, namely, for burning incense, and another for burning flesh (Exod. XXVII, XXXVII). The first altar was outside; the second was within the Holy of Holies. The first altar, therefore, is the compunction of fear; the second altar is the compunction of love. The former belongs to those who mourn their sins; the latter to those who yearn with all their desires for eternal joys. The stones of the former are recollections of sins; the stones of the latter are meditations on everlasting joys. Therefore the teacher builds the first altar when he sets forth the faults which the sinner, when he beholds them in himself, groans over. Rightly also is compunction called an altar, because it offers incense. But when each person is pricked with compunction for a long time over his sins, he advances through repentance to the practice of confidence. For after the times of affliction, he begins to burn for eternal life, and he who formerly wept from dread of punishment now begins to weep even more abundantly over the delay of his reward. Therefore, since the first compunction of the elect is born from fear, while through the figure of the king and the people, preachers and their recently converted subjects are signified, Saul is said to have then first built an altar. But from the progress of some, a teacher is often inflamed to pursue the gains of others. ...