Sforno on Exodus 5:2/ספורנו על שמות ה׳:ב׳

1'לא ידעתי את ה; I have never heard of any Being which created something tangible out of an absolute nothing.

2וגם את ישראל לא אשלח, even if it could be proved that this Being you speak about does in fact exist, I will not release the Israelites on account of that new found wisdom.