Are you willing to vouch for him?

你愿意为他担保吗？

《牛津词典》

Kim's mother agreed to vouch for Maria and get her a job.

金的母亲同意为玛丽亚担保，好让她找到一份工作。

《柯林斯英汉双解大词典》

I said, yeah, I'm going to vouch for.

我说，是，我给他担保，因为我相信他。

youdao

Is there really no one from Cranbrook that Romney can persuade to vouch for him?

FORBES: Bullying and Mitt Romney's Empathy Problem

He will roll out respected moderate Republicans and even the Chamber of Commerce to vouch for his bank.

FORBES: Why We Don't Need An Infrastructure Bank? Japan Is Why

They are far less keen on having to vouch for banks outside Germany.

ECONOMIST: Plans for common supervision could easily turn messy