Thomas Manton comments,
Proverbs 18:1 Whoever isolates himself seeks his own desire; he breaks out against all sound judgment.
Proverbs 27:17 Iron sharpens iron, and one man sharpens another.
Ecclesiastes 4:9 Two are better than one, because they have a good reward for their toil. 10 For if they fall, one will lift up his fellow. But woe to him who is alone when he falls and has not another to lift him up! 11 Again, if two lie together, they keep warm, abut how can one keep warm alone? 12 And though a man might prevail against one who is alone, two will withstand him– a threefold cord is not quickly broken.
Hebrews 10:24 And let us consider how to stir up one another to love and good works, 25 not neglecting to meet together, as is the habit of some, but encouraging one another, and ball the more as you see the Day drawing near.