《史记·七十列传·孟子荀卿列传》
于是就回到家乡与万章等人整理《经》《书经》，阐发孔丘的思想学说，写成《孟子》一书，共七篇。
退而与万章之徒序诗书，述仲尼之意，作孟子七篇。
So he returned to his hometown and sorted out the "Classics" and "Book of Documents" with Wan Zhang and others, expounded on Confucius's ideological theories, and wrote the seven-part "Mencius" book.