swear on a stack of Bibles, to

To make a very serious, solemn pledge, especially that one is telling the truth. A hyperbolic reference to the traditional act of placing one's hand on a Bible while taking an oath, such as before a court proceeding. Janet has sworn on a stack of Bibles that she wasn't the one to betray me, and I believe her. I swear on a stack of Bibles that if I have a chance to help your campaign, I will.

to state something very earnestly, pledging to tell the truth. (~ a Stack of Bibles refers in an exaggerated way to swearing to tell the truth in court by placing one's hand on a Bible.) I swear on a stack of Bibles that I am telling the truth. Of course, I'm telling the truth. I swear on my mother's grave!

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]

If someone swears on a stack of Bibles that something is true, they emphasize their promise that it is true. Our leaders swore on a stack of Bibles there was plenty of oil, and, of course, we wanted to believe them.

To make a solemn oath. Traditionally a solemn declaration or affirmation was pronounced as being by some sacred being or object. This practice is perpetuated in modern courtrooms by swearing in witnesses, a procedure that involves laying their hands on a Bible and pronouncing “Do you swear to tell the truth, the whole truth, and nothing but the truth?” Swearing on an entire stack of Bibles thus is construed as carrying considerably more weight than swearing on just one book. An American colloquialism from the mid-nineteenth century, it was used by Billie Holiday in her 1956 memoir, Lady Sings the Blues: “Mom . . . swore on a stack of Bibles I was eighteen.”