YeHoVaH set Israel apart from all the nations in the earth to be unto Him a Kingdom of Priests, and an Holy Nation. His plan for Israel as a Nation and Kingdom of Priests was first revealed to Abraham, the first to be called a Hebrew and a Prophet.
As a set apart Holy Nation, birthed during Passover, the first to be set apart, among the set apart, was the firstborn male. The institution of the Priests to minister unto YeHoVaH instead of the firstborn and the role of the Prophet to speak for YeHoVaH have everlasting significance in millennia.