Who you worship is who you serve, and who you serve is who you obey.

The Catholic church changed the law of God from the seventh day sabbath, Saturday, to the first day of the week, Sunday --- Daniel 7:25

Matthew 4:10 KJV
[10] Then saith Jesus unto him, Get thee hence, Satan: for it is written, Thou shalt worship the Lord thy God, and him only shalt thou serve.

Luke 4:8 KJV
[8] And Jesus answered and said unto him, Get thee behind me, Satan: for it is written, Thou shalt worship the Lord thy God, and him only shalt thou serve.

Romans 6:16 KJV
[16] Know ye not, that to whom ye yield yourselves servants to obey, his servants ye are to whom ye obey; whether of sin unto death, or of obedience unto righteousness?

Gospel of God is to worship only God

Exodus 20:3 KJV
[3] Thou shalt have no other gods before me.

Exodus 20:4-6 KJV
[4] Thou shalt not make unto thee any graven image, or any likeness of any thing that is in heaven above, or that is in the earth beneath, or that is in the water under the earth: [5] Thou shalt not bow down thyself to them, nor serve them: for I the Lord thy God am a jealous God, visiting the iniquity of the fathers upon the children unto the third and fourth generation of them that hate me; [6] And shewing mercy unto thousands of them that love me, and keep my commandments.

Exodus 34:14 KJV
[14] For thou shalt worship no other god: for the Lord, whose name is Jealous, is a jealous God:

Deuteronomy 5:7 KJV
[7] Thou shalt have none other gods before me.

Deuteronomy 5:8-10 KJV
[8] Thou shalt not make thee any graven image, or any likeness of any thing that is in heaven above, or that is in the earth beneath, or that is in the waters beneath the earth: [9] Thou shalt not bow down thyself unto them, nor serve them: for I the Lord thy God am a jealous God, visiting the iniquity of the fathers upon the children unto the third and fourth generation of them that hate me, [10] And shewing mercy unto thousands of them that love me and keep my commandments.

The plan for salvation from eternal death was given by Jesus.
A man came to Jesus and asked him what he had to do to receive eternal life. Jesus told him to keep the commandments if he wanted to enter into life, eternal life.

Matthew 19:17 KJV
[17] And he said unto him, Why callest thou me good? there is none good but one, that is, God: but if thou wilt enter into life, keep the commandments.

People think they are worshipping God, but they are obeying and serving a false god and to serve is to worship, therefore they are worshipping a false god.

Matthew 7:21-23 KJV
[21] Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven. [22] Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works? [23] And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.

John 8:33-37 KJV
[33] They answered him, We be Abraham's seed, and were never in bondage to any man: how sayest thou, Ye shall be made free? [34] Jesus answered them, Verily, verily, I say unto you, Whosoever committeth sin is the servant of sin. [35] And the servant abideth not in the house for ever: but the Son abideth ever. [36] If the Son therefore shall make you free, (Then) ye shall be free indeed. [37] I know that ye are Abraham's seed; but ye seek to kill me, because my word hath no place in you.

Romans 6:16 KJV
[16] Know ye not, that to whom ye yield yourselves servants to obey, his servants ye are to whom ye obey; whether of sin unto death, or of obedience unto righteousness?