6:29. And the Lord spoke to Moses, saying: I am the Lord; speak thou to Pharao, king of Egypt, all that I say to thee.
6:30. And Moses said before the Lord: Lo I am of uncircumcised lips, how will Pharao hear me?
Exodus Chapter 7
Moses and Aaron go into Pharao: they turn the rod into a serpent; and the waters of Egypt into blood, which was the first plague. The magicians do the like, and Pharao's heart is hardened.
7:1. And the Lord said to Moses: Behold, I have appointed thee the god of Pharao; and Aaron, thy brother, shall be thy prophet.
The god of Pharao… Viz., to be his judge; and to exercise a divine power, as God's instrument, over him and his people.
7:2. Thou shalt speak to him all that I command thee; and he shall speak to Pharao, that he let the children of Israel go out of his land.
7:3. But I shall harden his heart, and shall multiply my signs and wonders in the land of Egypt.
I shall harden, etc… not by being the efficient cause of his hardness of heart, but by permitting it; and by withdrawing grace from him, in punishment of his malice; which alone was the proper cause of his being hardened.
7:4. And he will not hear you: and I will lay my hand upon Egypt, and will bring forth my army and my people, the children of Israel, out of the land of Egypt, by very great judgments.