self sacrifice for ulterior motives

Parshat Va'Era

In the second plague, Moshe and Aharon bring frogs forth from the water to disturb the Egyptians. Par'oh calls Moshe and Aharon and pleads with them to pray to Hashem to remove the frogs. Moshe says fine and asks when he should ask for them to be removed. par'oh responds they should be removed the next day.
That is very weird! He should have said daven to get rid of them right now. I want them gone in 10 minutes! Why did he only say to remove them "tomorrow"?
Par'oh, it seems was really angling to set up Moshe. The commentaries say Par'oh really thought Moshe was using some form of magic to do this and he had to do things within certain time parameters. Par'oh felt that by askign for him to do it tomorrow, Moshe would not be able to do it because it was outside of the time window and that would prove Moshe wrong.

Look at that. Par'oh was willing to suffer for at least another day, if not longer (if Moshe would not be able to do it "tomorrow", Par'oh would have to wait until the next time window, whenever that would come. He was willing to continue suffering (and make his people suffer) just for the slight chance that he could have an opportunity to prove Moshe wrong. Look how strong the motive of revenge is. What happens to me is not important, as long as I prove him wrong.