The readings at Matins on Easter Sunday are from a sermon preached by St. Gregory on the same feast in the basilica of St. Mary Major (an important liturgical station).
"You have heard, dearly loved brethren, how the holy women who had followed the Lord came to the sepulcher with sweet spices. They had loved Him in life, now they would serve Him with all care and tenderness in death. But these things happened in order to signify certain acts that must be done in holy Church. And thus it becomes necessary to hear what once happened so that we may know what we must now do by way of imitation.
"Therefore, when we who believe in the Lord who died for us come and seek Him, bearing the perfume of personal virtues joined to a reputation for good works, we do indeed come to His sepulcher bringing sweet spices. But those women who came with sweet spices, saw angels. This should make it immediately obvious that the citizens of heaven may be readily seen by such who go forth with the perfume of good acts and holy desires to seek the Lord.
"Moreover, we would do well to determine why it was that the angel was sitting on the right side. What indeed is signified by the left hand, if not this present life? and what by the right hand, if not eternal life? Accordingly we read in the Canticle of Canticles: His left hand is under my head and with His right hand He embraces me (Cant. 2: 6). Therefore, since our Redeemer had already passed beyond the corruption of present existence, the angel who came to announce His eternal life sat on the right side.
"He appeared clothed in a white robe because he announced the joys of our feast. The shimmering whiteness of his raiment indeed proclaims the splendor of our solemn festival. Is it really ours, or his? Surely the more correct answer would be: both his and ours. For the resurrection of our Redeemer is indeed our feast because it renders us immortal, but it is also a feast for the angels because their number was completed upon our admission into heaven."