God's Purpose in Pharaoh's Hardening

Exodus 11:9-10

And the Lord saide vnto Moses, Pharaoh shall not heare you, that my wonders may bee multiplied in the land of Egypt.

So Moses and Aaron did all these wonders before Pharaoh: but the Lord hardened Pharaohs heart, and he suffred not the children of Israel to goe out of his lande.