be only as good as (one's) word

To be only as decent, respectable, or reputable as one's ability to tell the truth or follow through on one's promises. I can't believe you lied to Lou. He's an old-school guy who thinks that everyone is only as good as their word, so it'll take him a good while to start trusting you again. I have my flaws, but people respect me because I never lie. I firmly believe that you're only as good as your word. You said you'd be there? Well, then, you better be there—a man is only as good as his word, after all.