“The Angel of the Lord appeared to him in a flame of fire from the midst of a bush.” (Exodus 3:2)
When Moses saw the burning bush, he drew near, he looked and beheld. He saw this GREAT SIGHT why the bush did not burn. Then, He heard God calling him.
The Lord chose Moses to send him to Pharaoh that he may bring His people out of Egypt. He surely SAW the oppression of His people and have HEARD their cry because of their taskmasters, for He KNEW their sorrows.