Today's first reading is a comparison of two revelations of God: the first is the revelation of God on Mount Sinai, replete with thunderbolts and earthquakes and all manner of very convincing evidence that God is taking the proceedings quite seriously. So seriously, in fact, that no one, not even a goat, could so much as touch the mountain. The whole thing was too much for the people, who all begged God to find a more subtle form of communication.
So God did. The author of the Letter to the Hebrews wants to remind us (or maybe convince us) that we have drawn near a new mountain, a new Jerusalem, a city where angels are gathered in festival, and the covenant blood of Jesus. Abel's blood had called out to God from the soil where it had been spilled by his brother; his blood called for vengeance. Jesus' blood calls out to the Father from the Cross, not in a wordless plea for vengeance, but in the eloquent prayer, "Father, forgive them."
It's still an "untouchable" situation; we can only access it now through faith. And in the Gospel, Jesus has the fledgling apostles go out on an initial mission, "preaching repentance." Maybe today would be a good day to reflect on the gift of faith, and to thank the Lord that even without the blazing mountain and trumpet blast, we have been given the grace to know him in this life.