Sforno on Exodus 11:9/ספורנו על שמות י״א:ט׳

1ויאמר ה' אל משה לא ישמע אליכם פרעה, G’d told him that the reason why Pharaoh would not react positively to Moses’ warning was simply that He, G’d, had stiffened his heart in order to be able to demonstrate more miracles. This was designed to teach both the Egyptians and the Israelites the multi-faceted power of G’d, as well as His goodness, as He had said: “you will know that I am Hashem.” (10,2) Moses and Aaron performed all these miracles in order to fulfill what G’d had wanted to demonstrate through human messengers. Now, that the time had come to punish the Egyptians, not to demonstrate miracles, and to save the Israelites, i.e. at least the ones that deserved being saved, and also to destroy the Egyptian deities, G’d introduces the part the Passover was to play in this end-game. This portion commences with 12,12-13. G’d wanted that the command-ment of the Passover be communicated to the people by both Moses and Aaron so that just as Moses and Aaron both had had a part to play in their confrontation with Pharaoh, they should also have a similar part to play in getting the Israelites to perform the two commandments which would qualify them to take advantage of Pharaoh’s downfall, i.e. their own salvation, the Exodus. Only in this way would Moses and Aaron reap the reward of all their efforts so far.