What was the job Mr. Marvel chosen for?

Mr. Marvel was chosen to be the Invisible Man's errand boy.... something like an assistant. He wants Marvel to do the things that he is unable to do.

"I want you to help me get clothes--and shelter--and then, with other things. I've left them long enough. If you won't--well! But you will--must."

"Look here," said Mr. Marvel. "I'm too flabbergasted. Don't knock me about any more. And leave me go. I must get steady a bit. And you've pretty near broken my toe. It's all so unreasonable. Empty downs, empty sky. Nothing visible for miles except the bosom of Nature. And then comes a voice. A voice out of heaven! And stones! And a fist--Lord!"

"Pull yourself together," said the voice, "for you have to do the job I've chosen for you."