Except until you get the money, you haven't paid the bill - you've at best shifted it. If you put it on a credit card, for instance, until you pay off the credit card, you haven't paid what you owe. The credit card company has paid the bill, and now you owe the credit card company (plus interest for them assuming your debt).

When you get that paycheck, only then can you actually pay your bills, to whomever holds your debt at the time. To put it another way - you can't pay someone if you don't have any money in hand.