Musar zu Schemot 10:24

Later, after experiencing the plague of darkness, Pharaoh humbled himself yet more and offered to let go all the people, women and infants included (10,24). He excluded only the livestock. He implied that the Israelites could take sufficient livestock with them to offer sacrifices. When he said: רק צאנכם ובקרכם יצג, "Only your sheep and your cattle has to stay put, he referred to the livestock that would remain after the sacrifices had been offered. The word גם in גם טפכם indicates that he had already conceded something else, namely the livestock required for the sacrifices, before conceding the departure of the infants. When speaking about צאן ובקר, Pharaoh added the word רק, "only," to show that he restricted the amount of sheep and cattle that could be taken. We now understand both the use of the word גם, which indicates an inclusion, and the word רק, which indicates an exclusion.