When the Lord first appeared to John on Patmos, he had been instructed to write what you see in a book and send it to the seven churches
(Revelation 1:11). So here John also dutifully picked up his pen to write down what he learned from the seven thunders. He was, however, forbidden from doing so: do not write it down.
The reason is that it is enough for John’ readers in the churches to know that God is acting for their redemption; they need not know exactly what God will do to bring out their redemption. God’s people trust that his way and work will be wise and beneficial.
4 And when the seven thunders had sounded, I was about to write, but I heard a voice from heaven saying, “Seal up what the seven thunders have said, and do not write it down.”