‘The seven thunders uttered their voices, and when the seven thunders uttered their voices I was about to write, and I heard a voice from Heaven saying, “Seal up the things which the seven thunders uttered and do not write them”.'
It is clear from this verse that John has been recording his visions as he saw them, but this time he is told to desist. In Isaiah 29:11 God declares Israel to be in a spirit of deep sleep so that even their eyes, the prophets, are ‘closed'. All vision has become to them as the words of a scroll that is sealed, that none can understand. Here the world is seen to be in the same state. Their state is such that they will not listen to what the thunders say, so the words of the thunders are sealed. God will not speak to those who will not hear.
This compares with the reason why the Lord spoke in parables, so that those who claim to ‘see', but will not respond, might not perceive (Matthew 13:13; Mark 4:11-12; Luke 8:10). So this is a pregnant way of saying that as the world is deaf to all God's pleadings, God withholds His voice. What the seven thunders said was addressed to mankind and not to His people, and is kept secret until the end. (Although Paul in 2 Corinthians 12:4 speaks of being caught up into Paradise and hearing unspeakable words which it is not lawful for a man to utter, it is doubtful if that is the case here. This is speaking of judgments so devastating that their description is withheld).