When the government passes a law, it must be enforced. The executive branch of the government then makes up the actual enforcement rules. It interprets the law and translates it into actual regulations.
The ObamaCare law was 2,000 pages long. That is just the beginning. Now the executive branch is building on its foundations.
In other words, what Pelosi really meant was you have to pass the damned law in order to find out what we’re going to put in it.