Albert Barnes Commentary Mark 7:19

"because it goeth not into his heart, but into his belly, and goeth out into the draught? [This he said], making all meats clean." — Mark 7:19 (ASV)

Entereth not into his heart. It does not reach or affect the mind or the soul, and consequently cannot pollute it. Even if it should affect the body, it still cannot affect the soul and consequently does not need to be cleansed by a religious ordinance. The notions of the Pharisees, therefore, are not founded in reason but are mere superstition.

The draught. The latrine.

Purging all meats. The word purging, here, means to purify or to cleanse. What is thrown out of the body is the unnutritious part of the food taken into the stomach. This process leaves only what is proper for the support of life, and therefore, it cannot defile the soul.

All meats. This refers to all food—all that is taken into the body to support life. The meaning is that the system or process by which life is supported purifies or renders nutritious all kinds of food. The unwholesome parts are separated, and only the wholesome parts are taken into the system.

This understanding aligns with all that has since been discovered about the process of digestion and the support of life. The food taken into the stomach is converted by the gastric juice into a thick pulp called chyme. The nutritious part of this is conveyed into small vessels and changed into a milky substance called chyle. This is then changed into blood, and the blood conveys nutriment and support to all parts of the system. The useless parts of the food are thrown off.