(Verse 30) - And when forty years  - At the age of 80 years. This, however, was known by tradition. It is not expressly mentioned by Moses. It is said, however, to have been after the king of Egypt had died (Exo. 2:23); and the tradition is not improbable.

In the wilderness of mount Sinai - In the desert adjacent to, or that surrounded Mount Sinai. In Exo. 3:1, it is said that this occurred at Mount “Horeb.” But there is no contradiction; Horeb and Sinai are different peaks or elevations of the same mountain. They are represented as springing from the same base, and branching out in different elevations. The mountains are a prodigious pile, comprehending many peaks, and about thirty miles in diameter. From one part of this mountain, Sinai, the Law was given to the children of Israel.

An angel of the Lord - The word “angel” means properly a “messenger” (see Matt. 1:20), and is applied to the invisible spirits in heaven, to people, to the winds, to the pestilence, or to whatever is appointed as a messenger “to make known” or to execute the will of God. The mere “name,” therefore, can determine nothing about the “nature” of the messenger. That “name” might be applied to any messenger, even an inanimate object. The nature and character of this messenger are to be determined by other considerations. The word MAY denote that the “bush on fire” was the messenger. But a comparison with the other places where this occurs will show that it was a celestial messenger, and perhaps that it was even a pre-incarnate appearance of Christ, appearing to take the people of Israel under his own charge and direction. Compare John 1:11, where the Jews are called “his own.” In Exo. 3:2, it is said that the angel of the Lord appeared IN a flame of fire; in Exo. 3:4 it is said that Yahweh spake to him out of the midst of the bush; language which implies that God was there, and which is strongly expressive of the doctrine that the angel was Yahweh. In Exo. 23:20-21, God says, “I send an angel before thee, to keep thee in the way, and to bring thee into the place which I have prepared. Beware of him, and obey “his” voice,” etc., (Exo. 23:23; 32:34; 33:2). In all these places this angel is mentioned as an extraordinary messenger sent to conduct them to the land of Canaan. He was to guide them, to defend them, and to drive out the nations before them. All these circumstances seem to point to the conclusion that this was no other than the future deliverer of God's people, who came then to take his people under his own guidance, as emblematic of the redemption of his people.

In a flame of fire - That is, in what “appeared” to be a flame of fire. The “bush” or clump of trees seemed to be on fire, or to be illuminated with a special splendor. God is often represented as encompassed with this splendor, or glory, (Luke 2:9; Matt. 17:1-5; Acts 9:3; 12:7).

In a bush - In a grove, or clump of trees. Probably the light was seen issuing from the “midst” of such a grove.  This is likely not a lone bush, as the movie, the 10 Commandments portrays it.  It was likely a grove of trees, with Christ its midst and speaking from within it.