This is an indication from Scripture that, when we are in the companionship and the fellowship of others, we tend to shape each other. We rub off on each other.
A clear illustration of this is our relationship with our children. When a child is born, he is not born with the inflections or the twangs of the area into which he is born. Nobody has to teach anybody how to speak "Brooklynese" or "Southern." The nasal tone or drawl just rubs off. The child picks it up. It is ingrained within him unconsciously.
The same principle is at work in terms of character and personality. We rub off on each other. Are we rubbing off on each other for good, or are we rubbing off on each other for evil? Are we lifting one another up, or are we pulling one another down? We do not have to try consciously to do either. It will just happen. The world, largely, does not care how it rubs off on others - except that human nature wants people to think well of it, even while it is doing evil.
But in our Christian fellowship, we have the responsibility before God to work to rub off on each other for good. As long as we are conducting ourselves aright, it will rub off in the right way. In other words, all we have to do is work on ourselves. If we work on ourselves, then the projection of the self, the spirit that will go out from us, will be right, and it will have the right kind of impact.
God intends that prayer be an act of a free moral agent who consciously chooses to fellowship with God for the development of their relationship and the completion of himself as an individual.
Do we realize that, when we pray, we are in the presence of God, and He has the opportunity to rub off on us? It seems so simple as to be almost unbelievable, but it is right. Some of His Spirit reaches out and begins to affect us for good. Prayer is a major tool in our spiritual development through God's rubbing off on us. All the while this is happening, our minds are being subtly shaped by Him because we are in His presence.