God forbid

Natsuo Kirinoの "OUT" を読んでいます。

"Did you get the money?"
"I've got it right here," he said. From his back pocket he produced a brown paper bag, the kind used for penny candy. "It's exactly six million; I told them we couldn't do it unless we got the whole amount up front."
"Well done," she said. "But what happens if, God forbid, the body's found later on."
"Then we'll have to give the money back. But there are still some people who'll wind up with egg on their faces and you can be sure they'll find other ways to make me pay."

"God forbid" は直訳すると「神が禁じる」で "God forbids" となっていないのも不思議です。何れにせよ慣用句的用法ですね。
辞書の説明を見ます。
・Collins Dictionary: If you say God forbid, you are expressing your hope that something will not happen.: [feelings]: If, God forbid, something goes wrong, I don't know what I would do.
・Cambridge English Dictionary: a way of saying that you hope something does not happen: If there was a fire, God forbid, we’d be able to respond to the disaster.
・Merriam-Webster: used in speech to say that one hopes a bad thing will not happen: Heaven forbid that something bad should happen.

なるほど、嫌な事が起きて欲しくない時に言う表現ですね。最後に引用した辞書の例文にあるように、Godの代わりにHeavenも使われるのですね。