The future Day of the LORD not only parallels the Pentecost at Mount Sinai, but it also goes far beyond it by many scales of magnitude. The writer of the book of Hebrews compares the two events. His argument runs like this: if the theophany at Mount Sinai was fearsome, how much more so the theophany of the Day of the LORD! The shaking that took place at Mount Sinai when God’s “voice shook the earth” will seem insignificant compared with the shaking of all things in the Day of the LORD. - D. Thomas Lancaster, Two Trumpets