And he said unto them, Let the LORD be so with you, as I will let you go, and your little ones: look to it; for evil is before you. Let the Lord be so with you - This is an obscure sentence. Some suppose that Pharaoh meant it as a curse, as if he had said, "May your God be as surely with you, as I shall let you go!" For as he purposed not to permit them to go, so he wished them as much of the Divine help as they should have of his permission.
Look - for evil is before you - ראו כי רעה נגד פניכם reu ki raah neged peneychem, See ye that evil is before your faces - if you attempt to go, ye shall meet with the punishment ye deserve. Probably Pharaoh intended to insinuate that they had some sinister designs, and that they wished to go in a body that they might the better accomplish their purpose; but if they had no such designs they would be contented for the males to go, and leave their wives and children behind: for he well knew if the men went and left their families they would infallibly return, but that if he permitted them to take their families with them, they would undoubtedly make their escape; therefore he says, Exodus 10:11, Go now ye that are men, and serve the Lord.