take someone's word for it
US /teɪk ˈsʌm.wʌnz wɜrd fɔr ɪt/
UK /teɪk ˈsʌm.wʌnz wɜrd fɔr ɪt/

1.
人の言葉を信じる, 人の言うことを鵜呑みにする
to believe that what someone says is true, without checking or proving it
:
•
I haven't seen the report, but I'll take your word for it that it's accurate.
報告書は見ていませんが、それが正確であるとあなたの言葉を信じます。
•
He said he finished all his homework, and I had to take his word for it.
彼は宿題をすべて終えたと言ったので、私は彼の言葉を信じるしかなかった。