"Every mile I go is another $10,000 at least for charity," Samson said. "That's very motivating.
"What keeps me going is doing something that most people think can't be done. Knowing all the workers are at the ballpark waiting to help give all that money away and all the charities are at the ballpark, waiting to receive all that money. It will keep me going the first 40 miles. I don't know about the last 12."
Samson will start running at 7 a.m. ET in Pompano, and hopes to end at 6:43 p.m. at the ballpark, roughly a half-hour before the Marlins face the D-backs.
In a pregame ceremony, all the workers who spent three years building Marlins Park will be on the field. The aim is to raise more than $600,000 for 10 charities. Each five-mile leg, Samson will be accompanied by a runner for a specific charity.
One of the charities is dedicated to Parkinson's Disease. Samson will be joined during his run by his childhood friend, Bret Parker, who has raised more than $100,000 for the Michael J. Fox Foundation.
"It's really amazing what the Miami Marlins and David are doing," said Parker, who was at the Marlins-Mets game on Tuesday at Citi Field. "First of all, honoring the workers who built that amazing stadium is just great. And the money they're raising for these 10 charities is really important.
"For myself, the Michael J. Fox Foundation for Parkinson's research has a personal meaningful for me, having been diagnosed with Parkinson's five years ago and only disclosing this as part of this run."
Samson ran as many as 30 miles three weeks ago. Actually, it was on March 31, the day before the Marlins faced the Yankees in an exhibition game at Marlins Park.
"It went well," Samson said. "I went to work an hour after I finished. The weather Friday is supposed to be hot, which will be difficult."