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

1.
tomar la palabra de alguien, creer a alguien sin pruebas
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.
No he visto el informe, pero te tomaré la palabra de que es exacto.
•
He said he finished all his homework, and I had to take his word for it.
Dijo que había terminado toda su tarea, y tuve que tomarle la palabra.