Voluntarily adopted worship , whether unbidden or forbidden, it is a worship based upon our likes and dislikes rather than the will of God. It is not in reality worshipping God, therefore God will not accept will worship . This is a worship that is void of a knowledge of the true and living God. It is based upon superstition, tradition and the imagination of men, not on a revelation from God. When men leave the teachings and example of the Bible for their own likes and dislikes, worship becomes vain and void.
Man is a dual being.
He has a spirit and a fleshly body. The flesh has needs and desires. Some are natural and needful, some desires are egotistical, self-willed and sinful. As we have noted above, some try to worship God from the fleshly nature. Man has a spirit.