The fifth commandment of the Church is, "To contribute to the support of our pastors". In the Old Law, God Himself had prescribed that those chosen to serve the altar, namely, the entire tribe of Levi, should be supported, not by the cultivation of lands assigned them, as the other tribes were, but by appointed offerings of the people: I have given to the sons of Levi, He said, "all the tithes of Israel for a possession, for the ministry wherewith they serve Me in the Tabernacle of the Covenant" (Num. XVIII, 21). In the New Law, the Church has made, in different nations and ages, such provisions for the support of the clergy as circumstances required. The precept itself is founded in the law of nature. For, as St. Thomas argues, reason dictates that, as those who watch over the common good, such as princes and soldiers, are entitled to a stipend for their support, thus also those who are employed in the worship of God for the benefit of the whole people, should be supplied by the people with what is necessary for their support.
He next explains more fully how this support is to be understood, saying: "A priest is appointed to be a sort of middleman and mediator between God and the people, as we read of Moses (Deut. V, 5, 27); and therefore it belongs to him to deliver the Divine decrees to the people; and again, that which comes from the people, in the way of prayers, and sacrifices, and offerings, ought to be paid to God through the priest. And therefore the offerings that are made by the people to God belong to the priests; not simply to convert them to their own use, but also to dispense them faithfully, partly by expending them on what belongs to Divine worship, partly on what belongs to their own maintenance, because 'Those that serve the altar partake with the altar' (1 Cor, IX, 13), partly also for the use of the poor, who are to be supported, so far as possible, out of the property of the Church, because our Lord also had a purse for the use of the poor, as Jerome says" (2a 2ae, q. 86; Aquin. Eth. II, p. 138).
350. In the New Law, Christ has made for the support of the clergy a similar provision to that made in the Old Law; for in sending His Apostles, He bade them rely for support on those to whom they should preach, reminding them that "The workman is worthy of his meat" (Matt. X, 10). St. Paul insists with much earnestness upon the corresponding duty of the faithful to support their pastors, saying: "Who serveth as a soldier at any time at his own charges? Who planteth a vineyard and eateth not of the fruit thereof? Who feedeth a flock and eateth not of the milk of the flock? . . . If we have sown unto your spiritual things, is it a great matter that we reap your carnal things? . . . They that serve the altar partake with the altar. So also the Lord ordained that they who preach the Gospel, should live by the Gospel" (1 Cor. IX, 7-14).
In the early ages of the Church, no certain amount was appointed as due to the clergy, but the spontaneous gifts of the faithful supplied what was needed. Later on, the payments of tithes, that is of a tenth part of the produce of the land, was required by many Councils, especially in the ninth century. The piety of kings and nobles, and of the faithful generally, endowed the churches and monasteries so richly in the course of time that there was enough for altar, priest, and religious, as well as for the poor. But at the time of the Reformation, those in power seized all those incomes and the estates themselves, wherever Protestantism gained the ascendency. In the countries that have remained Catholic, the governments have since seized upon the patrimony of the Church and of the poor. As a partial restitution for this, they now pay an annual salary for the support of the clergy. In this country, and in others similarly situated, there is no such provision made, and therefore the natural duty of supporting religion rests entirely on the faithful. By calling it a natural duty we mean that it is not merely a pious practice or a counsel of perfection, but that it so binds the consciences of Catholics that neglect in this matter is a sin, and may be a grievous sin.
This support of religion comprises: a) Adequate provision for a church and its appointments; for sacred vessels and all the other requisites of Divine worship. b) Decent sustenance of pastors, suitable, namely, to their character as Bishops and priests, and to their social standing as representatives of the Catholic religion before the world. c) The erection, equipment, and maintenance of schools for the religious education of the young. The Third Plenary Council of Baltimore directs (n. 202) that "much zeal and prudence should be employed to eradicate from the minds of the laity the notion that care of the schools concerns only those parents who directly and actually make use of those schools."