Let’s look at the first reading. In it Isaiah wrote that he was called to be a prophet in the year King Uzziah died. Now, the only numbering for years in ancient times was the number of years for which each monarch reigned. Since the records show the length of all the royal reigns from Jesus on back, experts, by adding up those years, can tell us that Uzziah died in 751 b.c..
Solomon’s temple, built two hundred years earlier in 950 b.c., was still standing in Isaiah’s time, and it was thought to be a replica of the temple where God lived in heaven. (We know this because, where Exodus, Chapter Twenty-Five gives the materials and the measurements of the temple and its ingredients, it was thought then that the chapter was giving the materials and measurements of the temple in heaven.)
We believe that Isaiah was actually called on by God, but we think then that his lively imagination filled in the details. All Middle Eastern religious legends saw heaven as a throne room above the clouds. That had Isaiah see the train of the Lord’s garment filling the temple. And, because the people believed it was death to see God directly, Isaiah saw the Seraphim using a pair of their wings to shield their faces.
Their cry of Holy, holy, holy in Hebrew was kadosh, kadosh, kadosh. It meant aloof, aloof, aloof: separated from everything in the unclean universe.
In Jeremiah’s account of his being called to be a prophet it was God himself who touched his lips, while with Isaiah it was hot coal that seared off all his mouth’s wickedness. “Nabi” the Hebrew word for a prophet, was originally a child’s word for a mouth. A prophet was one who lent his mouth to God to speak God’s words. If we are good boys and girls, we can be prophets, lending God our mouths to speak his words.