Hesiod, Works and Days 11 ff (translation Evelyn-White) (Greek epic C8th or C7th B.C.):
It was never true that there was only one Eris. There have always been two on earth. There is one you could like when you understand her. The other is hateful. The two Erites have separate natures. There is one Eris who builds up evil war, and slaughter. She is harsh; no man loves her, but under compulsion and by will of the immortals, men promote this rough Eris (Strife). But the other one was born the elder daughter of black Nyx. The son of Kronos, who sits on high and dwells in the bright air set her in the roots of the earth and among men; she is far kinder. She pushes the shiftless man to work, for all his laziness. A man looks at his neighbour, who is rich: then he too wants work; for the rich man presses on with his ploughing and planting and ordering of his estate. So the neighbour envies the neighbour who presses on toward wealth. Such Eris (Strife) is a good friend to mortals.