We may apply this to a young. If conducted carefully on the basis of shared values and truth then friendships formed in youth can last a lifetime and be very wonderful, but do not be naïve in making friends, so that you become closely linked to another person without really knowing them. There is something intoxicating about friendship in youth which carries us away on the crest of the wave with little thought about where it is leading. It could be based on some brief shared experience which is taken out of proportion. It flatters our pride to think we can form such deep relationships. That person is popular and we want to be seen to be their friend. But we do not realise there is a deeply unpleasant side to their character and sooner or later we will be faced with it. Will we then end that friendship, or will we be pulled over a boundary that we previously vowed we would never cross?
Our closest friends should be those who love Christ, for ultimately it is these that share the same values and will have the best influence on us. For the Christian to make deep friendships in the world is to ignore all that Scripture has said is in the heart of the unbeliever. Can we really control what they are and what they do by our friendship with them? If we form an alliance their unbelief will prove stronger than our faith. For this reason it is great foolishness for a believer to marry and unbeliever, since there will either be a parting of the ways later with much pain, or the believer may be partially or completely dragged back into the world.