If he promised to help, he will not gobackon his promise.
如果他答应帮忙，他就不会食言。
《新英汉大辞典》
2
You can't gobackon your words once you make a promise on something!
我们不能相信他，他这人总是说话不算数！
3
Cultivation of the charm of a woman is the woman, her punctuality, compliance with the promise, even if never to gobackon the difficulties encountered;