Open Exodus 4:21-23.
Moses sets out for Egypt to confront Pharaoh with YHWH’s claim of sovereignty over the Hebrew people:
Exodus 4:22–23 (ESV)
22 Then you shall say to Pharaoh, ‘Thus says the Lord, Israel is my firstborn son, 23 and I say to you, “Let my son go that he may serve me.”
The descendants of Jacob are God’s family. God has promised to restore the blessing of his governance to the nations through them. So God “fathers” the nation of Israel: they are born through the exodus.
What a joyful contrast: serving YHWH rather than Pharaoh. Liberated from oppressive human rule, they’re the first nation to be a kingdom of God.
Along with the privilege of being YHWH’s firstborn (the eldest son in God’s family), Israel had the responsibility to show the other nations the glory of their royal Father.
But Israel struggled with that glorious vocation, bringing shame on their Father:
Hosea 11:1–2 (ESV)
1 When Israel was a child, I loved him, and out of Egypt I called my son. 2 The more they were called, the more they went away; they kept sacrificing to the Baals …
That’s why they fell back under foreign domination again, unable to be God’s representative kingdom. The Davidic kings had served as God’s sons on earth, princes who represented the heavenly sovereign (Psalm 2). But the princes had been cut off: there was no representative kingdom of God on earth for 600 years.
Until Jesus is born. He came as heir to the Abrahamic promises (Matthew 1:1-5), son of the Davidic kingship (Matthew 1:6-11). He represented the divine presence on earth, called to undo Israel’s captivity (Matthew 1:12-23).
God’s people were ruled by a Pharaoh-like king, willing to kill the Hebrew boys to keep his power. So Jesus’ family took him to Egypt. The true “king of the Jews” (Matthew 2:2) entered into the captivity of his people to lead them out in a new kind of exodus from evil reign.
Matthew 2:15 (ESV)
This was to fulfill what the Lord had spoken by the prophet, “Out of Egypt I called my son.”
So, the Son who restores heaven’s reign over the earth (the kingdom of heaven) called on his people to fulfil their role as God’s firstborn son, so the nations “see your good works and give glory to your Father who is in heaven” (Matthew 5:16).
That was Israel’s original vocation. They were released from serving Pharaoh in slavery, to serve YHWH as his son.
Earthly rulers do not easily withdraw their hand, so YHWH used the language human kings understand. If Pharaoh refuses to release the true king’s son, Pharaoh’s son will not reign:
If you refuse to let him go, behold, I will kill your firstborn son.
It’s no idle threat — a hint of the final plague. Pharaoh will be given a dose of his own medicine. Death is the weapon tyrants understand.
Evil rulers do not easily bow to our heavenly sovereign. Yet, history will not end with the death of God’s firstborn.