CONTEXT Donne wrote this in the 1590s as a young law student at Lincoln's Inn, before his secret marriage destroyed his career. The Inns of Court were basically fraternity houses for ambitious young men—lots of drinking, theater-going, and calculated debauchery.
The poem is structured as a legal contract with Cupid. Donne offers a deal: let me sleep around without emotional consequences until my hair goes gray (>"When with my brown my gray hairs equal be"), and then I'll submit to twenty hours of love-torment for every hour of freedom now. The usury metaphor is precise—moneylending at interest was technically illegal for Christians but widely practiced. Donne's casting Love as a loan shark who'll eventually collect with interest.
The key demand is >"Only let me love none"—he wants physical affairs without attachment. Notice he's not asking for celibacy. He wants to >"travel, sojourn, snatch, plot, have, forget" but never feel anything. The sport he's rejecting isn't sex itself but emotional investment, whether with country girls, court ladies, or city women. Even hearing reports about a woman shouldn't >"transport" (carry away) his mind.
The final stanza reveals the trap: when he's old and actually inflamed with love, Cupid wins either way—either Donne's honor is destroyed or he suffers shame and pain. The last line's twist is brilliant: even if a woman loves him back now, he'll bear it—endure it like a burden. Mutual love is the disaster he's trying to avoid.