I would say that this verse is one of the most amazing verses in the Bible. Why? Because it mentions matters about which Christians can have great certainty. Their certainty concerns the person and mission of Jesus Christ. So the first detail we can ask ourselves is, Who is Jesus?
John says three amazing things about Jesus: he is the Son of God, he is the true God and he is eternal life. In order to grasp something of these three features, we can begin by thinking about what it means for Jesus to be the true God. This is a reminder of his uniqueness because there is only one God. It is also a reminder of his competence because he possesses the attributes, performs the actions, and plans the aims of God.
The attributes of God are many and Jesus possesses every one of them. We list those attributes in different ways, such as in the Shorter Catechism answer to the question, ‘What is God?’ ‘God is a spirit, infinite, eternal and unchangeable, in his being, wisdom, power, holiness, justice, goodness and truth.’ Jesus possesses those attributes. Of course, when we speak in this way, we find ourselves out of our depth. Yet we need to remember who Jesus is because there is always the danger of reducing him in our thinking.
The second detail mentioned about Jesus here is that he is the Son of God. Right away, we face another mystery because this title tells us that within the one God there is more than one person. Since Jesus is the Son, it means that there is also the Father. Of course, we know from elsewhere in the New Testament that there are three persons in the Godhead – the Father, the Son and the Holy Spirit. This title of Jesus informs us that he has always had a special relationship and a unique role as God the Son. His unique role as the Son is to reveal the Father, to show to his creatures what the Father is like. Jesus said this several times. For example, he said that whoever had seen him had seen the Father. He can reveal the Father because, as he said, he and the Father are one.
Thirdly, John says that Jesus is eternal life. Whatever else this involves, it is clear that Jesus is the source of all other forms of life. We have derived life – it is given to us; we have dependent life – we cannot maintain ourselves in it; and we have decaying life because of our sins. Angels have derived life, dependent life, but because they have not sinned they don’t have decaying life. Instead they have what we can call developing life – they get better in the sense that they grow in knowledge and in experience. The life of the Son of God is not derived, is not dependent, cannot decay and cannot decrease or increase. He is the perfect fountain from which other life comes.
Jesus is truly great.