Summary: How did God design us? He wants us to gather together in faithful fellowship groups that lead us to the fullness of Christ. Our friendships will impact us for faith or not. We must make choices of fellowship on purpose.
We were formed for fellowship.
When God created Adam the Bible tells us that God said, “It is not good for the man to be alone, I will make a helper suitable for him.” Genesis 2:18 (quickview) . This was the first time that, after God created anything, he looked at it and said that it is NOT good.
God know us. He knows what is good for us and what is not. He formed us for fellowship, not just with himself, but with one another. We are not designed to go through life alone. In all of us there is a deep need for fellowship with others. God’s original fellowship plan for humanity was one man and one woman. God also blessed them with these words: “Be fruitful and multiply and replenish the earth…” Genesis 1:28 (quickview) .
God started the first small group of two, blessed it to multiply and it grew into the billions of people we see today. Wow! What God blesses, is really blesses! We are all part of the same family of man, but within that huge family we gather into smaller and smaller groups. The basic small group of humanity is still the husband and wife. If they are blessed with children, that group grows in size and number. If not, they still have each other, and the family from which they came.
God is the author of small groups, and the family is not the only one He formed. In fact, the first thing Jesus did when he began his ministry was to form a small group of 12 men whom he designated Apostles. People were formed for fellowship from the start. But there’s a problem, isn’t there… we don’t always do it God’s way. And when we do things our own way and break His rules things don’t go well. Today, it is common that there are unmarried couples living together. God knows that this is bad for us and He commanded us not to do it. There are people who have sexual relationships without marriage, they share their own bodies with one another without any commitment to a life together. God knows that this is bad for us and He commanded us not to do it. What God blesses, He really blesses, but, listen to me now, what God curses, He also really curses. Small groups may be either blessed or cursed by God. It depends on whether they are walking in His will or not.
Proverbs 1:10-19 (quickview)  talks about small groups of sinners who recruit others to join them in their evil pursuits. The father says to his son, “Do not walk with them! Keep your feet from their paths!” Proverbs goes on to make clear what kinds of groups are blessed and what kinds are not. Sometimes, we must separate ourselves from those who are not blessed by God.
Psalm 1 (quickview)  says: Blessed is the man that does NOT walk in the counsel of the wicked, or stand way of sinners, or sit in the seat of mockers. These are all groups that are to be avoided. God does not want us to have fellowship with such as these and He makes that very clear. God knows that what we have fellowship with is what influences and shapes us. God’s word says: evil companions corrupt good morals. He doesn’t say that they might corrupt them; he says that evil companions corrupt good morals, meaning that they most certainly will corrupt them. Small groups made up of unchristian people will tend to duplicate themselves. They are like cancer cells in the body.