He also testifies Tuesday. Tomorrow's testimony is to the Senate Judiciary committee - based on who will be asking questions, I wouldn't hold my breath for tomorrow to be anything but CYA.
Tuesday though Horowitz is testifying to the House Judiciary Committee with Goodlatte at the lead. THAT'S likely to be the more explosive/better round of testimony.
https://judiciary.house.gov/press-release/house-judiciary-and-oversight-committees-to-hold-hearing-on-ig-report-examining-doj-and-fbi-actions-in-2016/