I'll take your word for it
When you don't want to prove something and just let someone else lie for you.
'I'll take your word for it' when my friend said he had a million dollars, even though he had a job.
'I'll take your word for it' when my dad said he could run a marathon, even though he couldn't run a mile.
'I'll take your word for it' when my sister said she had a pet dragon, even though it was just a lizard.