Psalm 89:27 Also I will make him my firstborn, higher than the kings of the earth.

Jesus is again in focus here. He is: the firstborn of the dead (Col 1:18), the firstborn of every creature (Col 1:15), firstborn among many brethren (Rom 8:29). However, firstborn also refers to his people. Those who have faith in him. And God spoke to the kingdom of darkness (Egypt) and said this:

Exodus 4:22-23 Then you shall say to Pharaoh, 'Thus says the LORD: "Israel is My son, My firstborn. [23] So I say to you, let My son go that he may serve Me. But if you refuse to let him go, indeed I will kill your son, your firstborn."'"

God slayed the firstborn of Egypt to bring freedom to his firstborn. Its a shadow of our freedom. Before you were in the firstborn of light, you were a firstborn of darkness. None of us could be in the firstborn of light until the old man, the carnal man, the flesh, the firstborn of Egypt is slayed and this is accomplished in Christ.

Through him, the firstborn of Egypt is slayed, so we can walk as a "firstborn from the dead" i.e. we are born again, into a new family, the of heaven. Selah!