Leviticus 11:2

It is worthy of remark, that before the flood the flesh of animals was not allowed for food. Genesis 1:29. After the flood a permission was given to eat flesh. Genesis 9:3. Here the LORD draws a line of distinction between clean and unclean. Certainly this was for a mark of distinction between the LORD'S people, Israel, and other nations. And it should seem that by tradition, or somewhat like it, the LORD'S people had been distinguished respecting their food from the days of Abraham. So we read, that the Egyptians would not eat bread with the Hebrews: Genesis 43:32. And probably this might have been derived from divine appointment, though we have no mention made of it; because we find that at the going into the ark, the LORD himself taught Noah concerning clean and unclean creatures. Genesis 7:2.