Proverbs 27:17 “As iron sharpens iron, so one person sharpens another.” 

Ecclesiastes 4:9-12 “Two are better than one, because they have a good return for their labour: If either of them falls down, one can help the other up. But pity anyone who falls and has no one to help them up. Also, if two lie down together, they will keep warm. But how can one keep warm alone? Though one may be overpowered, two can defend themselves. A cord of three strands is not quickly broken.”