三人寄れば文殊の知恵 (さんにんよればもんじゅのちえ): three heads are better than two; three ordinary people together have great wisdom; if three people gather; the wisdom of Manjushri

three heads are better than two; three ordinary people together have great wisdom; if three people gather; the wisdom of Manjushri

For pooling ordinary minds on a hard problem. Manjushri is the bodhisattva of wisdom, so the claim is that three heads borrow some of his.

A Japanese proverb (ことわざ)