You do yourself in this.

FACE. Wherein? for what?

SUB. Marry, to be so importunate for one,
That, when he has it, will undo you all:
He'll win up all the money in the town.

FACE. How!

SUB. Yes, and blow up gamester after gamester,
As they do crackers in a puppet-play.
If I do give him a familiar,
Give you him all you play for; never set him:
For he will have it.

FACE. You are mistaken, doctor.
Why he does ask one but for cups and horses,
A rifling fly; none of your great familiars.

DAP. Yes, captain, I would have it for all games.

SUB. I told you so.

FACE [TAKING DAP. ASIDE]. 'Slight, that is a new business!
I understood you, a tame bird, to fly
Twice in a term, or so, on Friday nights,
When you had left the office, for a nag
Of forty or fifty shillings.