a small favour I would like to ask (of) you

[ademoglu]

Hello,

I've come across the sentence below in the move 'EVIL UNDER THE SUN.' And I've difficulty in understanding why 'of' is used.

''But before that, there is a small favour I would like to ask of you.''

In the dictionary (http://idioms.thefreedictionary.com/ask+of), as is seen, the phrase is ''ask something of someone or something'' but not ''ask something someone or something.''

Here's where I am confused. Is it because of a relative clause? What if we don't put 'of':

- But before that, there is a small favour I would like to ask you.

Thank you.

 

[MikeNewYork]

We ask people questions. We ask favors of people.

 

[Raymott]

Colloquially, you can use 'of' or not. I'd say it's more grammatical with 'of'.
You're asking for a favour. You're asking a favour of someone.
"Could I ask you a favour?" is used, but seems deficient to me.