Two revealing, if largely unnoticed, moments came in the middle of FBI Director Jim Comey’s Wednesday testimony before the House Judiciary Committee. When combined, these moments prove that Mr. Comey gave Hillary Clinton a pass.

Congress hauled Mr. Comey in to account for the explosive revelation that the government granted immunity to Clinton staffers Cheryl Mills and Heather Samuelson as part of its investigation into whether Mrs. Clinton had mishandled classified information. Rep. Tom Marino (R., Pa.), who was once a Justice...