Trump has refused to release his tax returns, citing an IRS audit.
Trump stepped up his rhetoric against Clinton in the fight for minority voters.
Nigel Farage made an appearance with Trump at his Mississippi rally.
Clinton's lead has shrunk from earlier this month in the online poll.
The speech had previously been scheduled for Thursday in Colorado.
Those in the country illegally will "pay back-taxes," Trump said.
Jonathan Swan 08/24/16 06:52 PM EDT
The private foundation is at the center of the latest firestorm in the 2016 race.
Ed Feulner has joined the transition team.
Nigel Farage is expected to speak at Trump's rally.
"The polls do not know what is actually going to happen," the Brexit leader said.