The seven thunders appear in Revelation 10:1–7. In his apocalyptic vision, the apostle John saw a mighty angel striding the sea and the land with a scroll in his hand. The angel gave a shout like the roar of a lion, and then the voices of the seven thunders spoke. Just as John was about to write down what they said, a voice from heaven told him to “seal up what the seven thunders have said and do not write it down” (Revelation 10:4).
The incident of the seven thunderous voices occurs in the interlude between the sixth and seventh trumpets. The seven thunders are not just the usual noise of thunder but are thunder-like voices communicating a message. The Greek word translated “thunder” means “to roar.” Thunder is often a mark of judgment in Scripture as in 1 Samuel 2:10, 2 Samuel 22:14, and several more places in Revelation (8:5, 11:19, 16:18), so these seven powerful voices are crying out for God’s judgment upon the sinful earth. The thunder represents the voice of God. Psalm 18:13 says, “The LORD thundered from heaven; the voice of the Most High resounded.”
Further evidence of the seven thunders being the voice of God is in Revelation 4:5: “From the throne came flashes of lightning, rumblings and peals of thunder. Before the throne, seven lamps were blazing. These are the seven spirits of God.” Again the voice of God is depicted as thunderous rumblings that display the power, majesty and glory of our mighty Lord. In this verse, John saw a preview of the divine wrath to be poured out on the earth as described in full in Revelation chapters 6—19.
Just as John was about to write the words of the seven thunders, a voice from heaven commands him to seal up what was revealed by them. The same throne that issues forth lightning and peals of thunder issues a command to keep secret what the voices have revealed. The reason for the sealing is not given, but it could be that the judgment was simply too terrifying to be recorded. The content of the message is never revealed in Scripture, so we can’t speculate on it. The seven thunders are the only words in Revelation that are sealed.