Leviticus 11:13
And these are they which ye shall have in abomination among the fowls; they shall not be eaten, they are an abomination: the eagle, and the ossifrage, and the ospray, And these are they which ye shall have in abomination among the fowls; they shall not be eaten, they are an abomination: the eagle, and the ossifrage, and the ospray,
The verse belongs to the law given through Moses that distinguished permitted creatures from those whose flesh was pronounced unfit for food, declaring certain birds, including the eagle, unclean and an abomination not to be eaten. It was taught to Israel in the wilderness as part of health and sanitary principles preparing them to enter Canaan. The prohibition was not arbitrary but was given to preserve life and health, to lessen the harmful results of animal food, and to direct the people to simple, healthful food. These birds were not the best articles of food and are hurtful to health, filling and polluting the blood with impurities and shortening life.
If Israel had submitted to these wise prohibitions in diet, God would have removed everything injurious to health and suffered no sickness to be among them. Daniel and his companions refused meats prohibited by this law because eating them would have defiled him, seeking to preserve clear minds and sound physical health for God's service. The Pharisees perverted these restrictions and made them burdensome by adding minute rules and traditions beyond what was commanded, going to unwarranted extremes. They required all drinking water to be strained lest the smallest insect in it might be classed with the unclean animals.