Arrival At Mount Sinai And The Appearance of Yahweh on the Mount (Exodus 19:1-25).
This section is introduced by a summary (Exodus 19:1-2) which refers back to the details in Exodus 17-18. It was possibly the opening of a new papyrus scroll (or tablet) in his source to bring back to mind the stage reached in the last scroll. Compare here Exodus 6:28 to Exodus 7:1 with Exodus 6:11-13.