In Exodus chapter four, verse twenty-two, the firstborn indicates a special love and relationship with God. God claims Israel as His son. Later in a narrowing of the sonship theme, God calls the Davidic dynasty His son, and still next, in a further narrowing, He claims Jesus as His Son.
The Jewish concept of being the firstborn son receives a double portion of the inheritance. The eldest child was considered the favored one of God. Israel is not God’s one and only son, but Israel, like all of us, is adopted as God’s unique son, just like God chose Jacob as the firstborn over Esau even when he was not naturally first. Being firstborn is not the same as being the one and only son. There is a sense in which all nations are God’s sons, but because Israel was favored by God and chosen to be his special people, by the Jewish description, Israel was God’s chosen, firstborn son.
Today, the firstborn is the first child inborn from a couple through childbirth. They get the opportunity to establish the fundamentals for the child. Teach the infant how to function daily and interact with their parents. The firstborn commonly inherit the abundance set up from the family when they become of age. The child gets to adventure the benefits of being first with learning how to do basic things once they reach that level of maturity.
As mentioned at the beginning, God claims Israel as His son. Like Israel, He adopts us through His Son, Jesus. We have the opportunity to establish ourselves in God by reading His Word, obeying what it says, especially the New Testament, and being a doer of it. As we become believers and draw closer to God, He will guide us on how to function in society and experience the benefits of learning and abiding by His ways. Finally, we get to reap the benefits of following His commandments and continue to grow as we reach the level of maturity.