[God] wanted [the apostles] to recognize the Lord Jesus Christ as truly risen, who was truly born, truly suffered and truly died. The manifest truth strengthened  the blessed apostles and all the disciples who were frightened by his death on the cross and were doubtful about his resurrection. The result [of Christ’s Ascension] was they were not only afflicted with sadness but also were filled with “great joy” when the Lord went into the heights of heaven.

—Leo the Great, Sermon 73.3-4