How that he was caught up into paradise, and heard unspeakable words which it is not lawful for a man to utter. 2 Corinthians 12:4
And when the seven thunders had uttered their voices, I was about to write: and I heard a voice from heaven saying unto me, Seal up those things which the seven thunders uttered, and write them not. Revelation 10:4
A young lady I know prayed that God would reveal to her the utterings of the seven thunders in Revelation. She promised not to tell anyone about them. She was not told, but I can appreciate her desire to know. With all the things that are revealed in this wonderful book, there are things, revealed to John, that we are not yet to know.
I am surprised that we are told of the seven thunders at all. But we can be certain that there are even greater things in store than those which have been revealed. The timing of the coming of the Kingdom (Mark 13:32) was not known even by Jesus during his earthly life. So much for those who set dates today. They claim to know more than Jesus did.