1. A promise is worth a thousand dollars: a word is worth a thousand dollars. Describe keeping his word and keeping his word.
2. Keep your word: From making friends, keep your word. Although I say I haven't learned, I will call it learning.
3. A gentleman's word: describe that the speaker's words and deeds are consistent, and what he said will be fulfilled. A word from a gentleman is a promise, and you must do what you promised.