Empty Men Flock Together and the Proverb Found in All Three

"And empty men gathered themselves to Jephthah" (Judges 11:3). From where do we know this matter that people say: "A bad palm tree goes and attaches itself to a thicket of barren trees" [like draws to like]? This matter is written in the Torah, repeated in the Prophets, stated a third time in the Writings, taught in our Mishnah, and taught in a baraita. It is written in the Torah: "And Esau went to Ishmael" (Genesis 28:9). Repeated in the Prophets: "And empty men gathered themselves to Jephthah" (Judges 11:3). Stated a third time in the Writings: "Every bird dwells according to its kind, and a man according to his like" (Ben Sira). Taught in our Mishnah: that which is attached to the impure is impure, and to the pure is pure. And taught in a baraita: Rabbi Eliezer says, not for nothing did the starling go to the raven, but because it is its own kind.