In Deuteronomy 16:21-22 the children of Israel were told to worship God by not having any mixture of idolatry. There is a great deal of this kind of mixture in the Roman Catholic Church.
"You shall not plant for yourself an Asherah of any kind of tree beside the altar of Jehovah your God, which you will make for yourself" (v. 21). An Asherah was an image of a female deity, and the altar signifies the cross. Catholicism has brought in certain pagan things and added them to the cross to produce a mixture. Books such as The Two Babylons give the sources of the mixture in Catholicism.
The erecting of pillars was also prohibited. "Nor shall you erect for yourself a pillar, something which Jehovah your God hates" (v. 22).
In 17:2-7 we see that God's people were required to stone to death those who transgressed God's covenant and served other gods, bowing down to them or to the sun, the moon, or any of the host of heaven. In this way, the children of Israel would utterly remove this abomination, the evil, from the midst of the people.