If you don't keep promise, you are a faithless person.

如果你没有守承诺，你是不可信的人。

youdao

If you make a promise, you should keep it.

如果你许下一个诺言，你就应该遵守它。

《柯林斯英汉双解大词典》

Be honest and keep your promise.

要诚实并遵守你的诺言。

youdao

"Johnsy,dear," said Sue, "will you promise me to keep your eyes closed, and not look out the window until I am done working?

VOA: special.2009.08.01

He made me promise to keep his secret.

VOA: special.2009.07.25

I didn't stay home for long because I'd madeapromise to Bubba, and I always tryto keep my promise, so I went on downto Bayou La Batre to meet Bubba's family.

VOA: standard.other

She would promise one thing and then when the time came to keep the promise, she would change it or move it further away in time.

FORBES: Seven Economist Mistakes About Parenting

To be sure, Mr Obama has many excuses for failing to keep his promise.

ECONOMIST: Maybe that has become the wrong question for Barack Obama

In addition, a gold standard provides a transparent set of practices to keep the promise.

FORBES: The Dollar, Gold And The Quality Of Money