Albert Barnes Commentary Exodus 5:17

"But he said, Ye are idle, ye are idle: therefore ye say, Let us go and sacrifice to Jehovah." — Exodus 5:17 (ASV)

You are idle - The old Egyptian language abounds in epithets which show contempt for idleness. The charge was equally offensive and ingenious; one which would be readily believed by Egyptians who knew how much public and private labors were impeded by festivals and other religious ceremonies. Among the great sins which, according to Egyptian belief, involved condemnation in the final judgment, idleness is twice mentioned.