These ye shall eat of all that are in the waters: all that have fins and scales shall ye eat:
The instruction belongs to the directions given through Moses distinguishing clean from unclean foods, which allowed eating water creatures that have both fins and scales as those least objectionable for food. That permission was not an exercise of arbitrary authority but was given to preserve life and health. Its purpose was to keep the blood pure through simple, healthful food so that the powers of mind and body would be retained, while the foods prohibited were those likely to make the blood impure and shorten life. Later leading Jews and Pharisees distorted this distinction by carrying it to unreasonable lengths with excessive requirements, turning life into a burden of ceremonies and restrictions that kept the mind under continual strain to discriminate between clean and unclean and to follow priestly injunctions, even to the point of straining all water lest the smallest insect or speck render it unclean and unfit to use.
The instruction belongs to the directions given through Moses distinguishing clean from unclean foods, which allowed eating water creatures that have both fins and scales as those least objectionable for food. That permission was not an exercise of arbitrary authority but was given to preserve life and health. Its purpose was to keep the blood pure through simple, healthful food so that the powers of mind and body would be retained, while the foods prohibited were those likely to make the blood impure and shorten life. Later leading Jews and Pharisees distorted this distinction by carrying it to unreasonable lengths with excessive requirements, turning life into a burden of ceremonies and restrictions that kept the mind under continual strain to discriminate between clean and unclean and to follow priestly injunctions, even to the point of straining all water lest the smallest insect or speck render it unclean and unfit to use.