13 And Samuel said to Saul, Thou hast done foolishly: thou hast not kept the commandment of the LORD thy God, which he commanded thee: for now would the LORD have established thy kingdom upon Israel for ever.
As, therefore, it was not lawful for one of another tribe, that was not a Levite, to offer anything or to approach the altar without the priest, so also do you do nothing without the bishop; for if any one does anything without the bishop, he does it to no purpose. For it will not be esteemed as of any avail to him. For as Saul, when he had offered without Samuel, was told, “It will not avail for you,” so every person among the laity, doing anything without the priest, labors in vain.
And Samuel said to Saul: You have acted foolishly, etc. And the Lord Himself in the Gospel, and the prophets, in their respective times, rebuke those who, as though sacrificing without Samuel, neglecting the help of the divine word, worship God in vain, teaching doctrines and commandments of men.
But if you had not done this, the Lord would have now prepared your kingdom, etc. This should not be understood as if God had established an eternal kingdom for Saul and later did not want to preserve it because he sinned, whom He had foreseen would sin; but He had prepared his kingdom in which there would be a figure of the eternal kingdom. But also every scribe instructed in the kingdom of heaven, bringing forth from his treasure new things and old, reigns over Israel forever (Matthew 11). Namely that Israel, which he made to be spiritual by teaching and ruling; to such people the apostle says, "For what is my crown or joy? Is it not you in the presence of our Lord Jesus?" (1 Thess. 2). Hence, to the servant who, trading well, that is, acquiring many through his teaching, it is said as he enters into the joy of his Lord: "You shall have authority over ten cities" (Luke 9); that is, from the merits and knowledge of those whom you have instructed spiritually from the law, you will shine more gloriously in the kingdom. But if some teacher has preferred his own understanding to the words of Scripture, and through those doctrines which he himself has composed, has led his listeners to carnal things rather than spiritual things; which is as Saul offering sacrifices without Samuel, sanctifying his army for battle, the foolish one will lose the kingdom. But if he had not done this, he could have had an eternal kingdom over Israel. About such people, the Savior in the Gospel: "Whoever therefore breaks one of the least of these commandments, and teaches men so, shall be called least in the kingdom of heaven" (Matthew 5). For such a person is the least in the present kingdom of the Church, entirely foreign to the future one.
[AD 380] Apostolic Constitutions on 1 Samuel 13:13-14