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Church comes from the Greek word ecclesia which simply means a gathering of believers. Churches teach that the Law has been done away with. Can you murder now, or covet, or bow down to other gods?
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Yes, we are saved solely by faith in the Isaiah 53 Savior. However, He said "If you love Me, keep My Commandments." His Commandments are the same as His Father's as They are One. . The Bible says that the Almighty "will not alter what goes out of His mouth." If that is not true, the Bible is not reliable. At Mt. Sinai, to the ears of the terrified Israelites below, He audibly spoke the 10 Commandments. This included a Fri. nightfall to Sat. nightfall Sabbath. NOTHING in the Bible says the Sabbath was changed to Sunday..
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People say "Paul said....Paul said..." But Paul said to follow the Savior, not him, and anyway Paul never said the Sabbath was changed and certainly had no authority to change what was audibly spoken by our Creator and written on stone with His very finger. When he said "Let no man judge you" he was talking to new converts and encouraging them in their observance, not NON observance, of the Biblical holy days, i.e. to not give into pagan peer pressures.

. Throughout the New Testament you can see that the apostles, including Paul, actually kept the Mosaic Law. In Acts 15, for example, "even" the food laws are upheld and yes, for NON Jewish converts. We see there that blood is still forbidden and that the new converts are expected to be, as was the tradition, in Synagogues, on the Sabbath, to learn the rest of the Law of Moses. In Acts 21 we see that Paul, and all those in the Jerusalem Council, upheld the Law of Moses and Paul took an oath to demonstrate that.
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Read the false accusations spoken against Stephen. He was falsely accused of saying that our Savior came to do away with the Law of Moses. Acts 6:11-14. Further, our Savior affirmed the Sabbath by telling his followers, about the time when the Temple would be destroyed - after His Ascension - "Pray that your flight will not be in the winter or on the Sabbath." He wanted them to be able to rest on the Sabbath in the future, as always in the past. . You can see some RCC leaders online admitting to the fact that the Bible does not sanction a Sunday Sabbath, but that Protestants keep it anyway since - guess who changed it? ROME, under the pagan sun worshipper Constantine, changed it over a millenium ago. Constantine said that Christians were to be executed if they kept the true Sabbath and said they needed to rest "on the venerable day of the sun." Check it out.
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Sun...day. It's not the Sabbath. However, the Father of Mercies knows we are all confused children. We need not to turn on others about it, therefore, but to show love. If we do not, no matter what we do it's all a waste, certainly not the path to Heaven. Yet, if you want to move away from "traditions of men" to the real truths of the real Bible, I recommend 119 Ministries' vids, starting with The Pauline Paradox. . And yes, you can rest or worship on any day of the week, but you are not supposed to...work...or cook...on the Sabbath - neither you nor those in your home, nor any servants (think waitresses and sales clerks etc.). Not even animals are to work then, or be penned up then. In fact, in Isaiah we are told to keep the Sabbath holy unto the Lord and also not to buy or sell on that day.
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The Sabbath is the longest Commandment and is stated in the Bible to be the very sign given to Israel of their Covenant with Him. (The New Testament tells us to be grafted into what? Israel.) Other nations had laws against murder and theft for example. Only those who wanted to Covenant with YHWH, aka God, were asked to keep the Sabbath. In the New Testament we are told to be grafted into Israel.. The 4th Commandment is not a suggestion. And no, I'm not a 7th Day Adventist. You don't need a "religion". You just need the Bible and the Father, the Son and the Holy Spirit.