Three months after leaving Egypt, the Israelites arrive at Sinai.
God tells Moses to assemble everyone for a big announcement. But one thing: they can't come up onto the mountain (where Moses chats with God) or they'll die. Noted.
Everyone washes up to look nice for the party.
God descends upon the mountain in fire, smoke, and eerily loud trumpet blasts.
God tells Moses, "Do not let either the priests or the people break through to come up to the Lord; otherwise he will break out against them" (19:24). Notice here that access to God is restricted to the few. For a guy who wants to adopt these people as his own, God doesn't seem to want to get too close to them.