While John’s account of Jesus’ life and ministry does not have a story about the birth of Jesus, John does give us an important insight into who Jesus is. Perhaps the clearest statement is John 1:14:
The Word became flesh and made his dwelling among us. We have seen his glory, the glory of the One and Only, who came from the Father, full of grace and truth. (NIV 1984)
The word translated “One and Only” here is often translated “only begotten” in several translations, such as in John 3:16 the way many of us memorized it. Even though Luke uses the word in three different stories about parents who were concerned about their only child (the widow whose only son died in Luke 7; Jairus’ daughter in Luke 8; and the man whose son was possessed by a demon in Luke 9), the word also seems to have a special meaning beyond “only child.”
In Hebrews 11:17, the writer refers to Isaac being Abraham’s “one and only son,” but we know that Abraham was also the father of Ishmael. Although Isaac was technically the older brother, he was also unique. This seems to be the special understanding of the word, which comes out in the context of the passage:
By faith Abraham, when God tested him, offered Isaac as a sacrifice. He who had received the promises was about to sacrifice his one and only son, even though God had said to him, “It is through Isaac that your offspring will be reckoned.” Abraham reasoned that God could raise the dead, and figuratively speaking, he did receive Isaac back from death. (Hebrews 11:17-19, NIV 1984)
Here we find that Isaac was the unique son of Abraham because he was the “son of the promise,” an idea Paul emphasized in Romans 4, 9, telling us that
Not all who are descended from Israel are Israel. Nor because they are his descendants are they all Abraham’s children. On the contrary, “It is through Isaac that your offspring will be reckoned.” In other words, it is not the natural children who are God’s children, but it is the children of the promise who are regarded as Abraham’s offspring. (Romans 9:6-8, NIV 1984)
Between these two passages about Isaac, we find the key to John’s description of Jesus.
Isaac is the “son of the promise” in two ways. First, he was the son who was promised by God to Abraham when he had no children, when he and Sarah were beyond the age of having children; yet, there he was. Second, he was the son through whom God promised to save his people (Genesis 21:12). In these ways, Isaac was a sign of the coming messiah, Jesus Christ.
Jesus, the One and Only, the Son of the Promise, is unique; he is set apart and holy. As John tells us, Jesus, the One and Only, reveals God’s glory, God’s truth, and God’s grace. By his birth, we see God’s holiness revealed for God’s glory and for our own new birth as God’s children.
In both of the genealogies of Jesus (Matthew 1; Luke 3) we can see how Jesus is “Abraham’s offspring,” and through the rest of the New Testament, we can see how everyone who puts their faith in Jesus become God’s children, as Paul writes in Galatians 4:28, “Now you, brothers, like Isaac, are children of promise” (NIV 1984). In the birth of Jesus, we find not only the One and Only Son of God but the gift who gives us the ability to become God’s children, as well. As we prepare to celebrate the birth of Jesus, let’s remember the holy, unique Son of God who makes us God’s children.