He won't dare to break his promise.

他不敢食言。

《牛津词典》

You mustn't break your promise.

你一定不能违背诺言。

youdao

We break our promise not to fly after hearing about a neighbor's trip to India.

听说邻居要去印度旅行后，我们违背了不坐飞机的承诺。

youdao

The LDP will hold over his head the threat of a no-confidence motion should he break his promise.

ECONOMIST: An unusual militancy is creeping into mainstream politics

In this, the president has been aided by his supporters in Congress, who, in helping him keep his ill-conceived promise to shutter Gitmo, have simultaneously enabled him to break his promise to "shine a light on the business conducted inside" the White House.

CENTERFORSECURITYPOLICY: A darker shade of transparency

Faraone's son Osiride wants to keep the Israelites around and continue his clandestine love affair with the Israelite Elcia, so he urges Faraone to break his promise and ends up a casualty of the last plague, the Slaying of the First-Born.

WSJ: Still Searching for the Promised Land | Moses in Egypt | New York City Opera | Opera Review by Heidi Waleson