Charles Ellicott Commentary Exodus 10:8

"And Moses and Aaron were brought again unto Pharaoh: and he said unto them, Go, serve Jehovah your God; but who are they that shall go?" — Exodus 10:8 (ASV)

Moses and Aaron were brought again to Pharaoh. —Moses and Aaron had uttered their threat, and had immediately left his presence. The courtiers “brought them again to Pharaoh.” The courtiers, no doubt, supposed that the king would yield; and the king was prepared to yield to a certain extent. But he had conceived of a compromise in his own mind, and this he hoped to impose upon Moses; hence his insidious question—

Who are they that shall go? —Pharaoh had not until now raised this question. He had known well enough that the demand extended to all the people (Exodus 8:8); but now he pretends that there had been an ambiguity, and requires that it shall be cleared up. Moses gives him an answer (Exodus 10:9) which takes away all further pretense of doubt.