swear on a stack of Bibles

Idioms  

1. Promise solemnly that what one is about to say is true, as in I swear on a stack of Bibles that I had nothing to do with his dropping out. This term alludes to the practice of placing one's hand on a sacred object while taking an oath, which dates from the mid-10th century. It is still followed in courts of law where a witness being sworn to tell the truth places a hand on the Bible. [Mid-1800s]

---

Example Sentences

Marse Alfred, I will swear on a stack of Bibles high as the 'Piscopal church steeple, that Bedney Darrington gim'me that same blue hankcher, and he said he found it.

From At the Mercy of Tiberius by Evans, Augusta J. (Augusta Jane)