Matthew Poole and continuators on Exodus 8:18

18 And the Magicians did so with their inchantments to bring forth lice, but they could not : so there were lice upon man and upon beast.

(i. e.) Indeavoured to do so. Thus to enter, Mat. 7. 13. is put for striving to enter, Luk. 13. 24. Thus men are said to deliver, Gen. 37. 21. to fight, Ios. 24. 9. to return, Ios. 10. 15. when they onely attempted or endeavoured to do so. And therefore when it is said in any of the plagues that the Magicians did so, it is not to be understood, that they really did the same thing, but that they indeavoured to do so, and that they did something which looked like it.

It was as easie for them to produce lice as frogs, but God hindred them, partly to confound them and their devilish arts, and to shew that what they did before was onely by his permission, and partly to convince Pharaoh and the Egyptians of their vanity in trusting to such impotent Magicians, and in opposing that God who could controll and confound them, when he pleased.