Seneca · On philosophy and friendship
Letters 9.6
If you ask how one can make oneself a friend quickly, I will tell you, provided we are agreed that I may pay my debt at once and square the account, so far as this letter is concerned. Hecato, says: “I can show you a philtre, compounded without drugs, herbs, or any witch’s incantation: ‘If you would be loved, love.’” Now there is great pleasure, not only in maintaining old and established friendships, but also in beginning and acquiring new ones.
Seneca, Letters to Lucilius 9.6, translated by Richard Mott Gummere