2. I can vouch for him/his honesty. 我可以为他[他的诚实]作担保。
3. I can vouch for his honesty. 我可以为他的诚实做担保。
英英解释
v.
1. give personal assurance; guarantee
2. give surety or assume responsibility
3. summon (a vouchee) into court to warrant or defend a title
4. give supporting evidence