That having the eyes of your heart enlightened. "The eyes of your heart" is an unusual expression, but it denotes that to see things clearly there is needed, not merely lumen siccum, but lumen madidum (to borrow terms of Lord Bacon), not merely intellectual clearness, but moral susceptibility and warmth—a movement of the heart as well as the head (compare the opposite state, "blindness of the heart," Ephesians 4:18).
Ye may know what is the hope of his calling; the hope which he calls you to cherish. The glory which he invites you to look forward to, when Christ shall come again, how sure it is and how excellent!
How infinitely it surpasses all earthly glory! How it at once ravishes and satisfies the heart! And what the riches of the glory of his inheritance in the saints. If the saints form God's heritage (see Ephesians 1:11), it may be asked Where are the riches of God's glory in them?
But it is not necessary to take the ἐν τοῖς ἁγίοις so literally. It may be rendered, "in reference to the saints." The riches of the glory of his inheritance in reference to the saints is the riches of the glory of their privileges as the Lord's heritage, or people; that is, their privileges are glorious.
But this glory is not limp, limited—it is wonderfully rich, full, abundant. God gives liberally—gives as a King, gives glory to all Christ's people. "When Christ, who is our life, shall appear, then shall ye also appear with him in glory" (Colossians 3:4); "The glory which thou gavest me I have given them."
The difference between this glory and ether glory is, human glory is often unjustly accorded, it passes away with wonderful quickness; but this glory is real and everlasting. "When the chief Shepherd shall appear, ye shall receive a crown of glory that fadeth not away."