After the initiation into priesthood, Aaron made the first burnt offering. Aaron’s sons Nadav and Avihu also made an offering incorrectly which resulted in a strange fire that consumed them both.
The laws of Kashrut are commanded. Animals that are clean can be consumed. Land animal has split hooves and chews its cud and fish with fins and scales are clean. Birds of prey, storks, pelicans, herons, ravens, ostrich, and seagulls are not clean. Locusts, crickets, and grasshoppers are clean. Other swarming 4 legged insects are not. Animals that walk on paws are unclean as well as those that creep on the earth.