your, his, etc. word of honour
(one's) word (of honor)
One's sincere promise or vow (about or to do something). I will be in that court to stand by your side during the trail—I give you my word of honor. After the president broke his word about lowering taxes for middle-class earners, I vowed never to vote for him again.
See also: word
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
your, his, etc. ˌword of ˈhonour(British English) (American English your, his, etc. ˌword of ˈhonor) used to refer to somebody’s sincere promise: He gave me his word of honour that he’d never drink again.
Farlex Partner Idioms Dictionary © Farlex 2017