When we were kids, if one told another kid something, they might insist that you swear it was true.
You would put your hands over your heart and say: “Cross my heart and hope to die.”
Meaning, if you were not telling the truth, may the Lord strike you dead.
Also, a common bedtime prayer went as follows:
Now I lay me down to sleep.
I pray the Lord my soul to keep.
If I die before I wake,
I pray the Lord my soul to take.
— Roger W. Smith