One interesting byproduct of being multilingual (or perhaps of just being at a certain point in your language studies) is that sometimes you'll just hear or read something and matter of factly wonder how that translates into your other language(s). Not because it's of any consequence, and it may just be a passing ponderance. If you're anything like me, though, it's a fairly common thing.
I was in church the other day and the responsorial was "If today you hear his voice, harden not your hearts."
Harden not your hearts, eh? Pretty cool phrase. I wondered what it was in Japanese, but was in no position to look it up. So I forgot pretty quickly. But I have remembered! Providence?
First off, a little research reveals that the passage of interest is from Psalms 95:
Today, if only you would hear his voice,
8 “Do not harden your hearts as you did at Meribah,
as you did that day at Massah in the wilderness,
Righto. Let's look up the Japanese!
The Japanese uses a literal parallel - 「心をかたくなにする」。 But this appears not to be the only way to translate the expression. ALC, I summon thee!
One of these in particular is pretty interesting! 「心を鬼にする」
「鬼」is a somewhat versatile word that can mean anything from "goblin" to "ogre" to "demon." Here we have it in verb form, which I've never seen before. So this expression is literally something like "Make your heart ogrish." Ogre up that heart!