The archway verse chosen here is interesting. It clearly applies to the ascension, but was spoken in a couple places at the Last Supper. “The time has come for me to return to Him Who sent Me. Do not be saddened nor let your hearts be troubled.” Use of these words at this moment shows that the whole of Jesus’ Paschal Mystery—from the beginning of the Passion to the present ascension—was one divine act of God. There was a unity to His work of redemption which He wrought in His Son. And here, in this blessed moment, we can also apply another verse from forty days prior: “it is finished,” this work of God.
Meanwhile, the Blessed Mother and the disciples are looking on in love and awe as Christ leaves them. Saint John kisses the robe of Christ one last time before he can no longer. “And it happened that, while He blessed them, He departed from them, and was carried up into heaven.” These words at the end of Luke’s Gospel surround our Lord in this image, and they remind us that even though Christ was no longer visibly present to His Church, His blessing remains, and is still present in those who watched this event take place. It is still present in the Church. Saint Leo reminds us too that this blessing is still given to us in the sacraments. Saint Peter’s keys especially remind us of all of this.
The angels above the archway look quite different than those we have seen in past mosaics. It’s likely that a different artist worked on this mosaic, but it makes me think that perhaps the resurrection of Christ was transformative for the choirs of angels in some way too, just as it was for all of this fallen creation. They speak to the apostles, who gaze up into the sky as Jesus ascends to the Father: “Men of Galilee, why do you stand gazing into the sky? This Jesus, Who is ascended, will return in the way you have seen.” The apostles cannot simply stand there. They have a mission! Christ has sent them forth, and they must go to “teach all nations, baptizing them.” We must go with them, for all must know of Christ and all He has done for us. “Rise, then, let us be going!”