4. Be particular and select, in the company which you keep, and the FRIENDSHIPS which you form.
“Tell me,” says the proverb, “what company you keep, and I will tell you what you are.” “Bad company ruins good morals.” (1 Cor 15:33) Vice is more easily and extensively diffused by improper companions, than by all other means. As one infected sheep communicates disease to a whole flock, so one sinner often destroys much good, by corrupting all the youth who fall under his influence. When wicked men are possessed of wit and fascinating personality, their influence is most dangerous to the young. We would entreat you, dear young friends, to form an intimacy with no one whose principles are suspicious. The friendship of profligate men is exceedingly dangerous. Listen not to their fair speeches, and warm professions of attachment. Fly from contact with them, as from one infected with the plague! Form no close alliance with such. No more think of taking them to your bosom, than you would a viper! Gaze not on their beauty, nor allow yourselves to be charmed with their fascination of manners. Under these specious appearances, a deadly poison lurks!
“Be not unequally yoked together with unbelievers”, (2 Cor 6:14) is the exhortation of Scripture. And what can be more unfitting and incongruous, than for an amiable and virtuous woman to be indissolubly united to an unprincipled debauchee? Or, for a good man to be married to a woman destitute of piety and virtue? Be especially careful, therefore, in forming alliances for life. Seek friendship with the wise and godly, and you will become wiser and better by converse with such.
– Archibald Alexander; Counsels of the Aged to the Young (See here for more info)