take my word for it

(idiom) trust me

Example Sentence:

If you want a great Greek restaurant, you should go to Maria’s. Take my word for it, it’s the best Greek place in the city!

A: Did you hear that Mark got fired?
B: Are you serious?
A: Yeah, he was caught stealing, so the boss fired him.
B: I don’t believe you.
A: Well, you should take my word for it, because he won’t be here tomorrow.