Exodus 8:18 - Clarke's commentary and critical notes on the Bible

And the magicians did so with their enchantments to bring forth lice, but they could not: so there were lice upon man, and upon beast. The magicians did so - That is, They tried the utmost of their skill, either to produce these insects or to remove this plague; but they could not, no juggling could avail here, because insects must be produced which would stick to and infix themselves in man and beast, which no kind of trick could possibly imitate; and to remove them, as some would translate the passage, was to their power equally impossible. If the magicians even acted by spiritual agents, we find from this case that these agents had assigned limits, beyond which they could not go; for every agent in the universe is acting under the direction or control of the Almighty.