Roger Stone will testify on July 24 in front of a closed session of the House Intelligence Committee as a part of its Russia investigation, per Politico.
His reasoning: Stone said that he wanted to speak out in order to rebut the testimony of Hillary Clinton's campaign chairman John Podesta, who appeared in front of the committee earlier today.
From the horse's mouth: In an email to Politico regarding his decision, Stone said, "I may not be able to sue a member of Congress but I sure as hell can sue the f--- out of Podesta. The claim that I had knowledge of the hacking of his email by WikiLeaks in advance is a demonstrable lie."