I'm writing a middle-grade novel in English. I have time-traveling kids from 1995 America who go to Ancient Egypt to join the Exodus. None of the kids speak anything but English (aside from a few words). The people they visit mostly speak Canaanite, an ancient form of Hebrew. (There are other languages there but let's put that aside.)
My big it's a fantasy book for kids for crying out loud handwave is that there is a magical invisible Universal Translator (think Doctor Who, but without any tech). To the kids, everyone's speaking English (though they know this isn't the case). To the locals, the kids speak and understand them just fine (though they might not know all the vocabulary). In reality, everyone's speaking the local language(s), languages the kids retain when they go home.
The locals are folks that love to sing and dance and I plan to put snippets of songs into the book. For some or most of them, I'll just use English. But a few of the songs will come from Jewish liturgy or straight out of the Torah. Or both, like in the case of Mi Chamocha (aka The Song of the Sea), a song of praise that the Hebrews sang after successfully crossing the Red Sea. The lyrics are right in the book of Exodus and it's a song we sing every week in synagogue.
I'd like those songs to be in Hebrew. I may also put in a few non-English words or phrases here and there. There are also some English words the locals will learn as they're non-translatable ("dude!").
I'll write it so that the readers don't have to run for a dictionary. Plenty of translations, etc. But this is a song that every synagogue-attending Jew (and every kid in Hebrew school) will recognize. Some of the words (just the main stanza) need to be from the original. (Note: while all my kids are at least part Jewish, none of them have attended synagogue and they don't know the songs.)
I will use transliteration only and it will be in Biblical Hebrew, which is not the same as modern Hebrew (though they're more or less mutually intelligible) and also not the same as Canaanite (I have no idea how close that one is).
How do I work this? Not just the weaving in of a foreign language but the idea that the rest of the book is written in English, even though they're not speaking English when they're in Egypt and thereabouts.