“When the LORD your God cuts off from before you the nations which you go to dispossess, and you displace them and dwell in their land, take heed to yourself that you are not ensnared to follow them, after they are destroyed from before you, and that you do not inquire after their gods, saying, ‘How did these nations serve their gods? I also will do likewise.’ You shall not worship the LORD your God in that way; for every abomination to the LORD which He hates they have done to their gods; for they burn even their sons and daughters in the fire to their gods. Whatever I command you, be careful to observe it; you shall not add to it nor take away from it.”
God knew the traps that Satan lays with alluring ways of worship. He warned His people not to neglect His clear instructions about how He wants to be worshipped. He tells us to never assume that He would like to be worshipped in the way those who worship other gods worship them.
Yet Israel continually fell into this trap, creating a syncretistic religion that combined some elements of biblical commands with the religious customs of the people around them.
Looking at the history of Christianity, it becomes evident that a similar process took place, as pre-Christian customs and celebrations were accepted by much of Christianity, though rejected by those who remained faithful to the teachings of the apostles and prophets.
For more about how pagan holidays began to eclipse God’s true and meaningful holy days, see From Holidays to Holy Days: God’s Plan for You.