I know what language they speak in Heaven.
Let me show you.
Revelation 19:1-2a reads:
After this I heard what seemed to be the loud voice of a great multitude in heaven, crying out,
“Hallelujah!
Salvation and glory and power belong to our God,
for his judgments are true and just;
The author, commonly thought to be St. John the Apostle, is looking into the end times with the help of the Holy Spirit, and the last judgments on the earth are about to be completed.
But look what he says in 19:1...
"After this I heard what seemed to be the loud voice of a great multitude in heaven, crying out,"
He's telling us what the voices from Heaven said, and that's all well and good, but the interesting thing is this word...
“Hallelujah!"
I thought that was an interesting word, so I dug into it a bit to see what I could find. The Greek word is "Ἁλληλουϊά," and in the ESV (English Standard Version, my preferred translation) the word appears exactly 4 times. All four of those occurrences are right here, in Revelation 19.
That can't be right, I thought. "Hallelujah" is a Hebrew phrase, meaning "Praise the LORD," or more specifically, "Praise Yah," where "Yah" is the poetic form of the Holy NAME of God.
But the Revelation was written in Greek, according to most scholars.
Well, I thought, surely it appears elsewhere in the Bible, possibly in the Hebrew?
Since the phrase means "Praise the LORD," I looked for that, and found the Hebrew phrase
הַלְלוּ־יָהּ
occurs 23 times in the Old Testament, all in the Psalms. The first occurrence is in Psalm 104:35, the final occurrence in Psalm 150:6. 150:6 is the final verse of the Psalms, and so the book ends with the phrase
הַלְלוּ־יָהּ, or "Praise the LORD!"
So, armed with this knowledge, I went back to the Revelation and looked more closely at the Greek.
The Greek word "Ἁλληλουϊά," pronounced "Alleluia," has no meaning.
None.
Then it hit me, suddenly; John is recording what he is hearing from Heaven. Ἁλληλουϊά is not a translation, it's a transliteration.
By this, I mean, John records the sound of the word he hears, rather than its meaning.
What sound did he hear?
הַלְלוּ־יָהּ
Hallelujah
Heaven speaks Hebrew.
The great Rabbi, Rashi, called Hebrew "לשון הקודש"... Lashon haKodesh. The Holy Language.
I completely agree.