The Assumption of the Blessed Virgin into Heaven
The Fourth Glorious Mystery of the Rosary is the Assumption of the Blessed Virgin Mary, when, at the end of her earthly life, the Mother of God was received, body and soul, into Heaven.
At the top of the window is a symbol of the lion of Judah. The Lion of Judah (Rev 5:5) is a symbol of the Israelite tribe of Judah in the Book of Genesis and a phrase in the Book of Revelation representing Jesus. Judah, son of Jacob the Israelite, was the progenitor of King David, and of Mary, the Mother of Jesus.
These lions are also flanking an ark, a symbol of Mary as the Ark of the Covenant. Thus, the lions are depicted as protecting the Ark of the Covenant, a reference to Christ watching over His mother.