|Lumen ad revelatiónem géntium * et glóriam plebis tuæ Israel.||A light for revealing to the nations * and the glory of your people Israel.|
To understand this phrase theologically we must first understand its grammar. What are lumen and gloriam doing here? Simeon has looked upon the infant and, speaking to God, calls Him salutare tuum, your salvation. Now he continues describing the same object (grammatically speaking, of course), using two other words. After seeing that Christ is the salutare of God, Simeon tells us that Christ is:
Lumen ad revelationem gentium = a light for revealing to the nations. Lumen is another neuter noun, which we must conclude appears here in the accusative case, giving us a string of three nouns, each of which are directly the object of viderunt: salutare, lumen, and gloriam. Simeon’s eyes have seen the salvation, the light and the glory. Note that gentium (from gens, gentis) is in the genitive plural, which would ordinarily be translated of the nations but in this special case we render it more smoothly into English as to the nations.
gloriam plebis tuae Israel = the glory of your people Israel. The Gospels teach of false and true glory. Satan uses the word gloriam to describe the glory of the kingdoms of earth, and offers to bestow this glory in exchange for worship of him. James and John covet sitting at Christ’s right and left when He comes in glory. But angels sing Glory in the Highest to God, and Christ speaks innumerable times of the true glory of the Kingdom of His Father. Simeon realizes, while Christ is still an infant, that Jesus Himself is the true Glory of God.