Symposium (Plato) 195e
ἐν γὰρ ἤθεσι καὶ ψυχαῖς θεῶν καὶ ἀνθρώπων τὴν οἴκησιν ἵδρυται, καὶ οὐκ αὖ ἑξῆς ἐν πάσαις ταῖς ψυχαῖς, ἀλλ᾽ ᾗτινι ἂν σκληρὸν ἦθος ἐχούσῃ ἐντύχῃ, ἀπέρχεται, ᾗ δ᾽ ἂν μαλακόν, οἰκίζεται.
(Roughly: For Love makes its home in the souls and dispositions of gods and men, and not in all souls equally, but when it should chance on one having a hard disposition, it flees; and when it chances on a soft one, it abides.)