Love itself, which can subsist under treachery, ingratitude, malice, and infidelity, is immediately extinguished by it, when perceived and acknowledged; nor are deformity and old age more fatal to the dominion of that passion.
 David Hume, An Enquiry Concerning the Principles of Morals (1751). copy citation

Context

“35.] , openly erected one altar to impiety, another to injustice, in order to bid defiance to mankind; even he, I am well assured, would have started at the epithet of FOOL, and have meditated revenge for so injurious an appellation. Except the affection of parents, the strongest and most indissoluble bond in nature, no connexion has strength sufficient to support the disgust arising from this character. Love itself, which can subsist under treachery, ingratitude, malice, and infidelity, is immediately extinguished by it, when perceived and acknowledged; nor are deformity and old age more fatal to the dominion of that passion. So dreadful are the ideas of an utter incapacity for any purpose or undertaking, and of continued error and misconduct in life!
When it is asked, whether a quick or a slow apprehension be most valuable?” source