M2:1530 — از محبت تلخها شیرین شود / از محبت مسها زرین شود

This couplet appears in the story of Luqman, specifically when he is being tested by his master. Luqman is offered a bitter melon, and instead of complaining, he eats it with gratitude. When questioned about his ability to consume such a bitter fruit, Luqman explains that he has received so many blessings and sweet things from his master that it would be shameful to complain about one bitter experience. He then attributes his ability to endure the bitterness, and even perceive it as sweet, to the profound love and gratitude he feels. This couplet encapsulates that sentiment, stating that love is the alchemical force that transmutes bitterness into sweetness and base copper into noble gold. It's not merely about enduring the bitter, but about love's capacity to fundamentally change one's perception and experience of it, making it sweet in the light of overwhelming generosity and affection.