New Defender's Study Bible Notes
19:18 mount Sinai. There has been much disagreement about the identification of Mount Sinai (same as Mount Horeb). The traditional site is the 7300 foot volcanic peak called by the Arabs, Jebel Musa (Mount of Moses), which overlooks a large plain where the children of Israel could have camped.
19:19 voice of the trumpet. There seems to have been a host of angels present around Mount Sinai as the Law was being given (note Acts 7:53; Galatians 3:19) and one or more were blowing loudly on the trumpet of God. This, along with the lightning and dark cloud and great quaking of the mountain, made an awe-inspiring spectacle which the people could never forget (or so it would have seemed). Compare the exposition of this scene in Hebrews 12:18-21.
19:24 the priests. This is the only mention of priests in Israel prior to God’s instructions for ordaining Aaron and his sons to the priesthood. Possibly this is a reference to the judges (Exodus 18:25-27) serving as a temporary body of priests along with Aaron until the more formal investiture of Aaron and his sons.