他向我保证这种事情绝不会再发生。

He gave me a guarantee that it would never happen again.

《牛津词典》

你曾向我保证今晚会早回家的。

You promised me (that) you'd be home early tonight.

《牛津词典》

他急忙向我保证没有任何不快的事要报告。

He hastened to assure me that there was nothing traumatic to report.

《柯林斯英汉双解大词典》

And I said to my advisor, "No, no. I have taken chemistry in high school, and I can assure you that chemistry has no relevance whatsoever to the life sciences."

于是我就去和我导师说：,“我在高中学过化学，我向你保证化学和生命科学,没有任何关联“

麻省理工公开课 - 化学原理课程节选

In other words, if I'm a rich, wealthy person in Corinth, I would say, "I'll be the local tax collector, and I'll guarantee you I'll send to Rome this amount of money for a year."

换句话说，如果我是科林斯的富人，我会说，“我想当本地税吏，我保证每年向罗马缴纳多少多少钱“

耶鲁公开课 - 新约课程节选

And I promise, this is the last quantum number that we'll be introducing.

我向你们保证，这是我们最后遇到的一个量子数。

麻省理工公开课 - 化学原理课程节选