your, his, etc. word is your, his, etc. bond
(one's) word is (one's) bond
One always keeps one's promises. I promise that I'll be there in time with the money for the deposit: my word is my bond. My word is my bond—I will be in that court to stand by your side during the trial. If Tom said he'll be here to help you move, I'm sure he'll be here—his word is his bond.
Farlex Dictionary of Idioms. © 2022 Farlex, Inc, all rights reserved.
your, his, etc. ˌword is (as ˌgood as) your, his, etc. ˈbondused to say that somebody always does what they promise to do: Don’t worry, you can trust my brother. His word’s as good as his bond.
Farlex Partner Idioms Dictionary © Farlex 2017