Why was Joseph sent ahead of his family to Egypt?
God sent Joseph ahead of his family to Egypt to preserve them, to establish a posterity in the earth, and to save their lives by a great deliverance. This was God's sovereign providence, preparing everything so the family would survive and the plan of salvation could ultimately be brought about through Christ.
Les explains that although Joseph's brothers hated and rejected him, and as far as they were concerned put him to death, God in His providence had prepared everything. Joseph declares that God sent him before his family to preserve a posterity in the earth and to save their lives by great deliverance. Les connects this to the Lord Jesus, who also had to go through rejection to bring about the whole plan of salvation, die for us, and extend salvation by grace. God is sovereign in everything He does.
And God sent me before you to preserve you a posterity in the earth, and to save your lives by a great deliverance.