Proverbs 13: 20
20 He that walketh with wise men shall be wise: but a companion of fools shall be destroyed.
Note, 1. Those that would be good must keep good company, which is an evidence for them that they would be good (men’s character is known by the company they choose) and will be a means of making them good, of showing them the way and of quickening and encouraging them in it. He that would be himself wise must walk with those that are so, must choose such for his intimate acquaintance, and converse with them accordingly; must ask and receive instruction from them, and keep up pious and profitable talk with them. Miss not the discourse of the elders, for they also learned of their fathers, Ecclesiasticus viii. 9. And (Ecclesiasticus vi. 35), Be willing to hear every godly discourse, and let not the parables of understanding escape thee.
2. Multitudes are brought to ruin by bad company: A companion of fools shall be broken (so some), shall be known (so the LXX.), known to be a fool; noscitur ex socio–he is known by his company. He will be like them (so some), will be made wicked (so others); it comes all to one, for all those, and those only, that make themselves wicked, will be destroyed, and those that associate with evil-doers are debauched, and so undone, and at last ascribe their death to it.
– Matthew Henry Commentary