“These things indeed have an appearance of wisdom in self-imposed religion, false humility, and neglect of the body, but are of no value against the indulgence of the flesh.”
“and neglect of the body”
The word “neglect” means severity, hard treatment, unsparing treatment. Severe self-control suggests an ascetic and unsparing attitude toward the body. The Greeks used harsh control over the body to build courageous exposure to hardship and danger. Here it refers to the ascetic discipline or severe self-control, suggesting an ascetic and unsparing attitude of religion.
Legalists neglect the body by abstaining from food. They kill bodily pleasures and appetites, but there is nothing of true piety in these things. The Bible teaches us to worship God in spirit and truth and not by ritual and taboos.
The principle of grace does not involve harsh treatment of the body.
Christianity is not self-induced misery. Fasting, going without food, and the ordinary things of life or any system that involves self-affliction to gain God’s favor violates the grace of God. Fasting is not wrong. Fasting to gain God’s favor is wrong.
Jesus did all the suffering necessary. He placated God sufficiently by his death on the cross to gain God’s favor. If Jesus won God’s favor, we violate him if we independently try to win that favor by ourselves.