In Yosh's answer to the question What are the ways to express someone's condolences?, this link states that Buddhist terms should not be used in expressing condolences to a Christian in Japanese:
故人がキリスト教徒の場合
仏教用語を使わないように注意しましょう。
※主な仏教用語 「お悔やみ」 「冥福」 「成仏」 「供養」 「弔う」 「仏」 「僧」
If this is accurate, I've been looking at this list of condolences and this one, and I see very little that could be used. Almost all of the samples include 「お悔やみ」 and a phrase such as 「安らかにご永眠されますようお祈りいたします」 or 「故人のご冥福をお祈りいたします」, which could potentially be appropriate for a Christian recipient who is Roman Catholic but do not sound appropriate for a Protestant (Protestants differ theologically on what happens to a soul/body after death, but generally do not believe the departed souls need to be prayed for. In English-language Protestant condolences, it is common to express that you will pray for the family of the deceased in this difficult time).
I have been informed by a Japanese Congregationalist (a type of Protestant) that his father (who was a Congregational church pastor, 会衆派教会のキリスト教徒) just passed away.
How can I alter
ご尊父様のご逝去を悼み、謹んでお悔みを申し上げます。
ご遺族皆様のお気持ちを思いますと心が痛みます。皆様のために祈っています。
to make it appropriate for a Protestant recipient?
