水心あれば魚心（みずごころあればうおごころ）

Japanese vocabulary

Meaning: kindness begets kindness; you scratch my back and I'll scratch yours; if the water is kind to the fish, the fish will be kind to the water

See it used in real works

• Example sentences from Japanese novels & web fiction (Massif)
• Hear “水心あれば魚心” pronounced in real videos (YouGlish)