Did God need to create us to get glory? In one way, this question is very simple: no he didn’t. But in another way, it’s a little more complicated.
The reason it’s complicated is because the Bible tells us why God created the world: He created it for his glory. In Isaiah 43:6-7, God says, “Bring My sons from far away, and My daughters from the ends of the earth—everyone called by My name and created for My glory”. Psalm 19:1 tells us that even creation and “the heavens declare the glory of God”. Contrastly, Paul explains that sin at its root is failing to bring glory to God — for though mankind “knew God, they did not glorify Him as God or show gratitude…Claiming to be wise, they became fools and exchanged the glory of the immortal God for images resembling mortal man, birds, four-footed animals, and reptiles” (Rom 1:22-23). And “all have sinned and fall short of the glory of God” (Rom 3:23). So we were created to glorify God, and humanity fell because we all failed to do this.
But there is another side to this question that we need to address; because we must assume that God did not have to create anything to be anymore glorious than he already is. Jesus, while praying before his death, says in John 17:5, “Father, glorify Me in Your presence with that glory I had with You before the world existed“. Jesus makes an important clarification, that the Godhead already had glory before the creation of the world. The Trinitarian community had eternal, infinite, unceasing glory before any of us ever existed. Paul says in Acts 17:24-25, “the God who made the world and everything in it—He is Lord of heaven and earth and does not live in shrines made by hands. Neither is He served by human hands, as though He needed anything”. So God is not served by human hands, and he does not need us. This means that creation couldn’t possibly add to God’s eternal glory even if we wanted it to. God’s glory is totally self-sustained within his triune existence.
So while the Bible affirms that God created all things for his glory, it also affirms that God has sufficient glory within his Trinitarian being to never create a single thing! How do we reconcile these two truths?
I think the key here is to see creation is an overflow and expression of God’s glory. What I mean is that because God had such perfect love within himself, such infinite fellowship, and such eternal greatness, that it brimmed over. And the triune God wanted to create a world through which to further express and share this glory. So when the Bible tells us that we were created for God’s glory, it means that we were created to express and reveal this triune joy. We were created to be God’s icons, and to manifest the love so infinitely and perfectly expressed in the Godhead. In a very real way, all of creation is an overflow of the perfect triune life within God. That’s why we are created in God’s image (Gen 1:26-27). We were created to further manifest, display, and reveal the glory so greatly displayed in the triune God. This also makes sense when we consider God’s first act with Adam, which was to give him a person with which to share love and unity (Gen 2:24). Is not marriage a display of the unity and love found between the Father, Son, and Spirit? I think so. So creation then is an overflow, a brimming over, an expression and revelation of the glory already found in the Godhead.
John Owen explains this well, saying, “The Father’s love for the Son is the fountain and the prototype of all love…and all love in the creation was introduced from this fountain to give a shadow and resemblance of it”. Richard Sibbes also says, “the Father so enjoyed his fellowship with his Son that he wanted to have the goodness of it spread out and communicated or shared with others. The creation was a free choice borne out of nothing but love”.
For a more expansive view of how this affects our view of the gospel, and the purpose of the Christian life, I’d invite you to listen to this sermon I gave on God’s glory, The Purpose of the Christian Life.
John Piper also has a good small series of videos on this concept over at Desiring God: http://www.desiringgod.org/interviews/the-devotional-on-glory