What is attendance at false worship?
It is to assist at the religious worship of heretics. To worship God according to a rite contrary to all precepts of the Gospel is a false and unlawful worship of God. Hence it would be a grievous sin for a Catholic to worship God according to the ceremonial laws of the Jews, for though they were prescribed by God for the Jews before the coming of Christ, yet they were abolished by Christ in the new law.
It is also a false and unlawful worship of God to adopt a new religion in opposition to the doctrine of the true Church of Jesus Christ, the Roman Catholic Church, and assist at the religious worship of such a false religion. Hence, even if a Catholic despises in his heart such a false religion and worship, it is unlawful for him to play the organ, or to sing, or to discharge the office of sacristan, in Jewish or Protestant temples during their false worship, or to compose hymns or music for the same, or to ring the bell for calling the people together, or to contribute money towards the erection of temples for false worship, or to call a Protestant minister for the performance of some religious rites, as, for instance, the rites of marriage or baptism, or funeral, etc.; or to take Protestant children, or accompany grown persons, to Protestant Sunday-schools or church and stay with them during their religious worship. Any such act is strictly forbidden by the law of God and of the Church, because it is a real communication and formal co-operation in a false worship, and a real approval of it.
"No one" say the Fathers of the Fourth Council of Carthage (in 398), "must either pray, or sing psalms with heretics; and whosoever shall communicate with those who are cut off from the communion of the Church, whether clergyman or layman, let him be excommunicated." Such was the language of the Church in all ages.
Pope Paul IV. wrote to the Catholics in England : "We are forced to admonish and to conjure you, that on no account you go to the churches of heretics, or hear their sermons or join in their rites, lest ye incur the wrath of God, for it is not lawful for you to do such things without dishonoring God and hurting your own souls." In consequence of such authoritative decision, the Catholic pastors of England and Scotland have made most strict prohibitions of all such communication by their special regulations.
Here one may say : The reason why I play the organ, or sing, or officiate as sacristan, etc., in a Protestant church, is because I get a good pay which enables me to support my family. I answer: What you do is a grievous violation of the first commandment. It is never allowed to commit a mortal sin in order to acquire the means of support. Alas ! that there are so many people who make a living by unlawful means ! "But the bishop, or parish priest has given me permission to play the organ, to sing, etc., in the Protestant church," says another one. I answer : Neither any priest nor bishop, nay, not even the Pope, can give you permission to violate any of the commandments. "But I am well instructed in my religion," says another; "I can see no harm in what I do in the Protestant church." I answer : I doubt what you say. If you were well instructed, you would know that attendance at false worship is a mortal sin, and that this sin is still greater for him who plays, or sings, at it, or renders any other kind of service for it. And do you see no harm in committing a mortal sin? Do you see no harm in the great scandal you give to those Catholics who know of it, and to the Protestants, whom by your playing and singing, etc., you confirm in the belief that their religion is as good as the Catholic religion ? (See Bishop Hay's Sincere Christian, Vol. II. On communicating with those out of the Church and Father A. Konings C. SS. R., Moral Theology, de Co-operatione Catholicorum. p., 136.)
St. Hermenegild, the son of Leovigild, king of Spain, became a convert to the Catholic faith. When his father, who was addicted to the Arian heresy, heard of it, he be came quite enraged, and put his son in a frightful dungeon, where he made him suffer most cruel torments. The holy martyr wrote to his father: "I avow your goodness to me has always been very great. I will preserve, to the last moment of my life, the respect, duty, and tenderness which I owe you. But is it possible that you should wish me to like worldly greatness better than my salvation ? I value the crown as nothing. I am ready to lose sceptre and life, too, rather than abandon the divine truth." The prison was a school of virtue to this great martyr. He clothed himself in sack-cloth, and performed other bodily penances in addition to the hardships of his prison. He offered up to God many fervent prayers to obtain sufficient strength and courage to remain faithful in confessing the truth and dying for it. The solemnity of Easter being come, the perfidious father sent, in the night, an Arian bishop with the message to his son that, if he received communion from the hand of that prelate, he would be received into favor again. Hermenegild, however, rejected the proposal with indignation, reproaching the messenger with the impiety of his sect, as if he had been at full liberty. When the bishop returned to the Arian king with this account, the furious father, seeing the faith of his son proof against all his endeavors to make him give up the Catholic religion, sent soldiers with orders to kill him. They entered the prison and found the saint fearless and ready to receive the stroke of death. They cleaved his head with an axe, and scattered his brains on the floor. (Butler s Lives of the Saints, April 13.)