kindness begets kindness; you scratch my back and I'll scratch yours
Proverb meaning that if you show goodwill to others, they will respond in kind. Often used to describe reciprocal relationships. The literal meaning is 'if the water has a mind for the fish, the fish will have a mind for the water'.
See also: 魚心あれば水心
Kindness begets kindness: since he was kind to me, I helped him in return.
In business, the spirit of mutual give-and-take is important.
Literally, “if the water shows goodwill, the fish will show goodwill”: 水心 and 魚心 personify the two parties in a reciprocal relationship.