Don’t be tricked 1 John is short but it packs a hefty punch. It doesn’t waste much space. I would recommend reading through it and start looking for reoccurring themes and phrases (“with,” “in,” “abide,” “fellowship,” “life”--to name a few). Also, don’t just think about 1 John as a stand alone letter so much of what he is says connects back with his gospel. The gospel is the foundation for what John is saying in his epistle.
I came across two instances where John points back to the foundation he laid in his Gospel. First, 1 John 2:15-17
Do not love the world or the things in the world. If anyone loves the world, the love of the Father is not in him. For all that is in the world—the desires of the flesh and the desires of the eyes and pride in possessions—is not from the Father but is from the world. And the world is passing away along with its desires, but whoever does the will of God abides forever.
Compare this passage with the famous
“For God so loved the world, that he gave his only Son, that whoever believes in him should not perish but have eternal life. For God did not send his Son into the world to condemn the world, but in order that the world might be saved through him.” (John 3:16-17).
Notice the similar words “world,” “love[d],” “whoever,” “abides forever” (cf. “eternal life” more on this later). “For God so loved the world, that he gave his only Son.” This sacrifice by the Father. This willing death by the Son is the embodiment of love. If “God is love” (1 John 4:8) then Jesus is God’s love. If you were to ask “How is God love?” then I would say, “Look to Jesus. Look to the cross.”
If what you heard from the beginning abides in you, then you too will abide in the Son and in the Father. And this is the promise that he made to us—eternal life. (1 John 2:24-25)
The promise that God made to us is “eternal life.” That sounds kind of un-reformed. What would John Piper say? Isn’t God the gospel? Aren’t we supposed to love Jesus more than our physical life and pleasures? Piper says,
The critical question for our generation--and for every generation--is this: If you could have heaven, with no sickness, and with all the friends you ever had on earth, and all the food you ever liked, and all the leisure activities you ever enjoyed, and all the natural beauties you ever saw, all the physical pleasures you ever tasted, and no human conflict or any natural disasters, could you be satisfied with heaven, if Christ was not there? (God is the Gospel p. 15. I use this more for illustrative purposes. I agree with Piper’s thrust.)
Are the two opposed? What does John say? Well in his Gospel he reports, “Jesus said to him, ‘I am the way, and the truth, and the life. No one comes to the Father except through me’” (John 14:6). He then says later in his epistle, “And this is the testimony, that God gave us eternal life, and this life is in his Son” (1 John 4:11). John says Jesus is the life. He is our eternal life. Our new life is wrapped up “in his Son.”
That’s the beauty of all the union / fellowship language in 1 John. Our identity. Everything about us. Our hope. Our current life. It’s all wrapped up impossibly with Jesus. So hoping for eternal life is nothing more than hoping for Jesus. Let that sink in.