This window depicts witnesses of Christ's Ascension into Heaven.
"When He had led them out to the vicinity of Bethany, He lifted up His hands and blessed them. While He was blessing them, He left them and was taken up into heaven."
Before he left, Jesus "opened their minds so they could understand the Scriptures" written in the Bible. Then he told them to travel out to all the nations, preaching about repentance and forgiveness of sins in Jesus' name.
Many years later, the Apostle Paul outlined that Gospel message in a letter to the Christian church in Corinth:
"What I received I passed on to you as of first importance: that Christ died for our sins according to the Scriptures, that he was buried, that he was raised on the third day according to the Scriptures, and that he appeared to Peter, and then to the twelve [Apostles]. After that, Jesus appeared to more than 500 of the brothers at the same time, most of whom are still living... Then he appeared to James, then to all the Apostles, and last of all he appeared to me also."
-1 Corinthians 15:3-8
The Irwin window was a gift of Mrs. Richard Hays in memory of Boyle Irwin (1772-1860), Elizabeth McCully Irwin (1786-1867), and Richard Hays (1815-1877).