肥水不流外人田

肥水不流外人田

Literally means:

fertilized water is to enrich one's own land and not be let out into other people's fields

Actually means:

benefits are to be shared exclusively among one's own people

肥水 refers to fertilized water in the fields.

Here it is a metaphor for benefits. This phrase figuratively means that benefits should be kept only for oneself or shared among his family.

肥水，农田里含有肥料的水，比喻利益或好处。

肥水不流外人田，比喻利益或好处只留给自己或自家人，不能给外人。