If Deuteronomy 14:19 says all flying insects that swarm are unclean, why does Leviticus 11:22 allow locusts to be eaten?

Locusts did not become clean at a later time. They were already listed by God as clean among certain kinds of winged insects. The apparent difficulty comes from comparing the wording of Deuteronomy 14:19 with the fuller explanation in Leviticus 11.

Deuteronomy 14:19 says, “And every creeping thing that flieth is unclean unto you: they shall not be eaten.” Taken by itself, this sounds like all flying insects were forbidden. However, Leviticus 11 gives the more detailed law. It says, “All fowls that creep, going upon all four, shall be an abomination unto you” (Leviticus 11:20). But then it gives an exception: “Yet these may ye eat of every flying creeping thing that goeth upon all four, which have legs above their feet, to leap withal upon the earth” (Leviticus 11:21).

Then God specifically names the permitted kinds: “the locust after his kind, and the bald locust after his kind, and the beetle after his kind, and the grasshopper after his kind” (Leviticus 11:22). These were clean because they had jointed legs for leaping.

So Deuteronomy 14:19 is a summary statement, while Leviticus 11 gives the fuller rule with the exception. The general rule was that flying creeping insects were unclean, but the leaping kinds, such as locusts and grasshoppers, were permitted.

This also explains John the Baptist’s diet. Matthew 3:4 says John ate “locusts and wild honey.” John was not violating God’s law. He was eating an insect that the law itself had allowed.

Therefore, locusts never “became” clean. They were already clean under the Mosaic food laws, while most other flying insects remained unclean.