That’s why Jesus warned us about worshiping Him in vain by keeping the commandment of man and not the commandments of God. Mathew 15:3-9 The Church who made this change freely admits changing God’s day from Saturday to Sunday was not based on scripture authority and they want you to know when worshipping God on the first day you are not obeying God but a commandment of the Catholic Church. Who should we obey God or man that Jesus warns us not to do?
It is well to remind the Presbyterians, Baptists, Methodists, and all other Christians, that the Bible does not support them anywhere in their observance of Sunday. Sunday is an institution of the Roman Catholic Church, and those who observe the day observe a commandment of the Catholic Church.
—Priest Brady, in an address, reported in the Elizabeth, NJ ‘News’ on March 18, 1903.
Protestants ... accept Sunday rather than Saturday as the day for public worship after the Catholic Church made the change... But the Protestant mind does not seem to realize that ... in observing Sunday, they are accepting the authority of the spokesman for the Church, the pope.
—Our Sunday Visitor, February 5th, 1950.
Of course these two old quotations are exactly correct. The Catholic Church designated Sunday as the day for corporate worship and gets full credit – or blame – for the change.
—This Rock, The Magazine of Catholic Apologetics and Evangelization, p.8, June 1997
Q. Have you any other proofs that they(Protestants) are not guided by the Scripture?
A. Yes; so many, that we cannot admit more than a mere specimen into this small work. They reject much that is clearly contained in Scripture, and profess more that is nowhere discoverable in that Divine Book.
Q. Give some examples of both?
A. They should, if the Scripture were their only rule, wash the feet of one another, according to the command of Christ, in the 13th chap. of St. John; —they should keep, not the Sunday, but the Saturday, according to the commandment, "Remember thou keep holy the Sabbath-day;" for this commandment has not, in Scripture, been changed or abrogated;...
—Rev. Stephen Keenan, A Doctrinal Catechism; New York in 1857, page 101 Imprimatuer
A. Had she not such power, she could not have done that in which all modern religionists agree with her; —she could not have substituted the observance of Sunday the first day of the week, for the observance of Saturday the Seventh day, a change for which there is no Scriptural authority.
—Rev. Stephen Keenan, A Doctrinal Catechism; New York in 1857, page 174