someone's word is their 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.
someone's word is their bondsomeone keeps their promises.
A variant of this expression, now rather dated, is an Englishman's word is his bond .
Farlex Partner Idioms Dictionary © Farlex 2017