Why did the early church write the new testament in books when God said it’d be written on hearts?

Question by Ataraxia: Why did the early church write the new testament in books when God said it’d be written on hearts?
Jeremiah 31:33

”But this is the covenant which I will make with the house of Israel after those
days,” declares the LORD,
“I will put My law within them and on their heart I will write it; and I will be
their God, and they shall be My people.”

The old covenant had its regulations written on stone and scrolls and books. The new one has regulations written on the heart of each participant. Its not to be externaized like the old one, not one to be told in word or writing by somebody… Do this, dont do that… The new covenant is the age of spiritual maturity, to be guided by conscience, not books.

Best answer:

Answer by Obnoxious Cole fan
I think that “on their hearts” was a metaphor. Uhm..Christianity would be a lot more hated if people wrote things on actual hearts.

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