Deuteronomy 14:18

And the stork, and the heron after her kind, and the lapwing, and the bat.

The stork, heron, lapwing, and bat stand in the list of creatures classed as unclean and prohibited for eating. The prohibition specifies which living creatures are least objectionable to be taken as food. The restriction was given to guard health and to preserve life. It was not an arbitrary exercise of authority. Eating the forbidden kinds pollutes the blood and shortens life. The simple, healthful food required instead keeps the blood pure, so that the powers of mind and body are retained.

The health law was afterward distorted by adding excessive rules, as in straining water to keep out tiny insects. Jewish leaders carried the requirement to unreasonable lengths, making life a burden of ceremonies and restrictions about eating and drinking, with continual straining over clean and unclean and a multiplication of priestly injunctions.