On the morning of the third day there were thunders and lightnings and a thick cloud on the mountain and a very loud trumpet blast, so that all the people in the camp trembled. Then Moses brought the people out of the camp to meet God, and they took their stand at the foot of the mountain. Now Mount Sinai was wrapped in smoke because the LORD had descended on it in fire. The smoke of it went up like the smoke of a kiln, and the whole mountain trembled greatly. And as the sound of the trumpet grew louder and louder, Moses spoke, and God answered him in thunder.
Exodus 19:16-19
According to promise (11) God manifested Himself on the third day, in an awesome demonstration of majesty and glory. We should compare this passage with the divinely inspired comment on it in Hebrews 12:18ff. In making the contrast between the old and the new, however, the Apostle does not mean to suggest that when the old covenant is superseded such a disclosure of the divine majesty is nullified as an experience for the Church. It is a misunderstanding of the contrast between the two covenants to suppose that that should ever change. Indeed, the need for the recovery of such a sense of the holiness of God is very great in our time. What do we suppose that Pentecost was for the first disciples? Was there not fear, as well as joy, in their experience? Think of the terror of the Damascus Road encounter or of John's on the Isle of Patmos. One has only to recall to mind the history of revival movements in the past two or three centuries to realise that the brooding of the Spirit of God has always produced this overwhelming sense of awe and fear and wonder. There are some things that the replacement of the old covenant by the new does not change, and the unchanging majesty of God is first among them. The trumpets sounding forth on the mount are doubtless those to be heard at the coming of Christ (1 Thessalonians 4:16; 1 Corinthians 15:52), and this association of ideas is some indication of the cardinal importance of the giving of the Law in the economy of God. It was undoubtedly an event of the greatest magnitude.