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Revelation 13 identifies the first and the second beasts. After careful study, it is manifest that the first beast is the papacy, and the second beast represents the United States of America. Both entities will work to implement the mark of the beast. The mark of the beast is the man-made law of the first-day observance instead of the seventh-day Sabbath of the fourth Commandment (Exodus 20:8-11). For more information on the Mark of the beast, check the following link: https://bibleask.org/what-is-the-mark-of-the-beast/
To answer your question: would working on the seventh-day Sabbath be sinful? God blessed the seventh-day Sabbath from the very beginning at the creation of the world “And God blessed the seventh day, and sanctified it…” (Genesis 2:3). And He commanded, “Remember the Sabbath day, to keep it holy. Six days you shall labor and do all your work, but the seventh day is the Sabbath of the Lord your God. In it you shall do no work…For in six days the Lord made the heavens and the earth, the sea, and all that is in them, and rested the seventh day. Therefore the Lord blessed the Sabbath day and hallowed it” (Exodus 20:8-11). So working on the seventh day Sabbath would be against God’s commandment.
There is not a single verse in the entire Bible that shows Sunday sacredness. Sunday observance is a man-made tradition that came about in the fourth century with the conversion of the Roman Emperor Constantine to Christianity. In order to make it more convenient for his pagan subjects to make the change to Christianity, Constantine accepted their day of worship, Sunday, instead of the Christian seventh-day Sabbath which had been observed by Jesus and all the prophets.
The contents of this article and website are not intended to be against any individual. There are many priests and faithful believers in Roman Catholicism who serve God to the best of their knowledge and are seen by God as His children. The information contained herein is directed only towards the Roman Catholic religio-political system which has reigned in varying degrees of power for nearly two millennia. This system has established an increasing number of doctrines and statements that directly go against the Bible.
It is our purpose to lay the clear Word of God before you, the truth-seeking reader, to decide for yourself what is truth and what is error. If you find anything here contrary to the Bible, do not accept it. But if you desire to seek for Truth as for hidden treasure, and find herein something of that quality and feel that the Holy Spirit is revealing Truth to you, please make all haste to accept it.