After three days of darkness, Pharaoh calls Moses back.
"Go, worship before the Lord; only your sheep and your oxen shall abide with me: your children also may go with you" (Targum Pseudo-Jonathan on Exodus 10:24).
Notice the movement. In the previous negotiation, Pharaoh had said: only the men may go. Now, under the weight of the ninth plague, he concedes that the children may go too. He has moved. But not all the way.
The Aramaic paraphrase, preserved in the Targum attributed to Yonatan ben Uzziel, renders the hostage-demand plainly. Lechod anachon v'torachon yit'akvun lvati — only your sheep and your oxen shall remain with me. Pharaoh is still insisting on collateral. If the livestock stays, the people will return. A free population without animals cannot survive in the wilderness. They would come back for the flocks, and the slavery would resume.
The Maggid teaches: partial freedom is another name for continued bondage. Pharaoh understands this better than almost anyone. He has watched Moses win concession after concession, and each time he has tried to keep one handhold — the women, then the children, now the flocks. As long as something of Israel remains in Egyptian hands, Egypt still holds Israel.
Moses will refuse this final handhold. The entire people, and every hoof they own, must leave. That is the only release worthy of the Name of the Lord.