One good turn deserves another.

A kindness, favor, or helpful act ought to be met with kindness in return. The saying presents reciprocity as a fair and socially expected response to someone who has done good for another person.

It can also encourage people to sustain mutual support: one helpful deed may prompt a second. The phrase expresses an ideal of willing repayment, not necessarily an equal exchange or an enforceable obligation.

Use it when acknowledging help and indicating an intention to repay it with a comparable kindness, or when urging reciprocal goodwill. It suits everyday conversation and writing about favors, cooperation, and considerate conduct; it need not imply that a favor creates a strict debt.