Today, we will discuss how we are to be distinct from the world while still being actively involved in it. Our ultimate example in this—and all things—is Jesus Himself.
The Jews believed in order to maintain purity and holiness, one must avoid contact with the world. That's why they were shocked when Jesus chose to eat with "tax collectors and sinners." Over the years, there have been leaders and entire so-called Christian sects that have isolated themselves from society to various degrees.
We can't imagine living like this. Yet, we disconnect from the world all the time. We avoid conversations with people we don't know. We talk about every topic except faith with family and friends. We surround ourselves with fellow believers. But authentic Christianity is more than simply being physically in this world; it's about engaging the world.
In Matthew 9:12, Jesus says, "Those who are well have no need of a physician, but those who are sick."
What good is a mechanic who doesn't repair cars? What good is a chef who doesn't cook? What good is a doctor who doesn't help the sick? And what good is a Christian who doesn't engage the world? If we want to be like Jesus, we also need to be in the world, not isolated from sinful people.
In John 15:15, Jesus says this to His disciples: "No longer do I call you servants, for the servant does not know what his master is doing; but I have called you friends."
Jesus ministered to unbelievers. He ate with them, healed them, and provided for them for the purpose of revealing Himself to them. But He didn't call them friend.
First Corinthians 15:33 says, "Do not be deceived: 'Bad company ruins good morals.'"
I'm not saying you can't call an unbeliever friend. One could argue that Jesus was being friendly to unbelievers by loving them. But Jesus had a mission when it came to spending time with unbelievers, and so do we.
Jesus came into this world to testify to the truth (John 18:38) and to seek and save the lost (Luke 19:10).
Jesus, in His prayer in John 17:18, says we should do the same. "As you sent me into the world, so I have sent them into the world."
The Father sent Jesus into the world to proclaim the message of salvation (John 3:16-18), and He gave us the same mission. So, we can be friendly with the world. We may even call an unbeliever friend, but we can't forget the God-given reason why we're friends with them.
In John 17:15, Jesus prays, "I do not ask that you take them out of the world, but that you keep them from the evil one."
First Peter 5:8 says, "Be sober-minded; be watchful. Your adversary the devil prowls around like a roaring lion, seeking someone to devour."
God's mercy and grace is clearly seen in Peter's life. Even though he denied Jesus three times … Even though he ran off and began fishing again after his Master was crucified … Still, the Lord restored Him. He used Peter in mighty ways to spread the gospel.
We must remember that we have been set apart from the world. The only way to experience real and lasting joy is to know the truth and walk in it. The happiness and pleasure Satan and the world offer are fleeting. We must turn our back on the lie that the world's way is the right way.
When we come to saving faith in Jesus, we're born from the Spirit, no longer of this world (John 3:1-8). We are set apart from the world that doesn't know God. Through this new birth, this new relationship, we are given a new nature that desires to please God. The only way we're able to overcome sin, to strive for holiness, to strive for unity, to be distinct from this world, is through the Holy Spirit who dwells within us.
This new relationship, this new nature, gives us a new purpose in life: to glorify Christ, not only in what we say and do but also by proclaiming the gospel to this lost fallen world. We no longer identify with the things of this world, but now identify as the people of God who were given to Christ before the foundations of the world. We will spend eternity with Him. 
Have you trusted in Christ and His shed blood on the cross as your only hope? Has the Lord changed your heart of stone into a heart of flesh? Has He changed your desires? Has He changed your motives? Has He changed what you love? The only true lasting hope, joy, and peace come from believing in Christ as your Lord and Savior.
Each of us needs to take some time to reflect on the text and then reflect on our own lives. If we trust in Christ as our Lord and Savior, then we must ask ourselves, "How much are we in the world? Do we rub shoulders with unbelievers so we can share the gospel with them? Are we too isolated?"
We can read, study, and believe God's Word all day long, but it doesn't matter if we're not sharing it. We can't share the gospel if we don't have contact with the world. But remember, being distinct doesn't mean living like unbelievers. Instead, we live for Christ in order to tell the world that Jesus saves.
 These points were inspired by A. W. Pink, Exposition of the Gospel of John