Go back on (one's) word

Перевод слова "go back on (one's) word" на Русский язык

нарушить (своё) слово

He promised to help us, but he went back on his word.

Он обещал помочь нам, но нарушил своё слово.

To fail to keep a promise or commitment; to break one's word or not do what one has said they would do.