hand to God

Used to emphasize that one is telling the truth, typically when their words are likely to be met with skepticism or disbelief. I was going to come to your party, hand to God! I just wasn't feeling well, that's all. I did push for you to get the promotion, hand to God! But the boss made the final call, and she picked George. A: "I didn't start that rumor about you, hand to God!" B: "Yeah, right. You've been trying to sabotage my student council campaign this whole time."