After God continued to fuck with freewill by making Pharaoh unable to care, not only for the Hebrews who wanted to be free, but also his own people, God continued to punish him with more plagues.

First came boils, then hail, then locusts, then darkness, until finally he decided to straight up murder every first born son in Egypt. The Hebrews who wanted to avoid losing their first born sons had to do a crazy ritual involving slaughtering a lamb and spreading its blood on the doorframe.