Exodus 10:7

For the first time the officers of Pharaoh intervene before the scourge is inflicted, showing at once their belief in the threat, and their special terror of the infliction. Also, for the first time, Pharaoh takes measures to prevent the evil; he does not indeed send for Moses and Aaron, but he permits them to be brought into his presence.

Let the men go - i. e. the men only, not all the people. See Exodus 10:8.