Homer, Odyssey 8.585-6

“A friend who knows you well is in no way less than a relative”

… ἐπεὶ οὐ μέν τι κασιγνήτοιο χερείων

γίνεται, ὅς κεν ἑταῖρος ἐὼν πεπνυμένα εἰδῇ.

(Yeah, the translation is a little loose. But I like it.)