This is the name of God that he revealed to his people in the Old Testament. See the translationWord page about Yahweh concerning how to translate this.
Since Nehemiah is speaking to Yahweh, the pronouns "him" and "his" can be translated as "you" and "your." Alternate translation: "who love you and keep your commandments" (See: [[rc://en/ta/man/translate/figs-123person]])