17 For what does He say Himself to the infirm, to the end that recovering that sight, they may be able in some measure to reach the Word by whom all things were made? “Come unto Me, all you that labour and are heavy laden, and I will refresh you. Take My yoke upon you, and learn of Me, that I am meek and lowly in heart.” What does the Master, the Son of God, the Wisdom of God, by whom all things were made, proclaim? He calls the human race, and says, “Come unto Me, all you that labour, and learn of Me.”
You were thinking haply that the Wisdom of God would say, “Learn how I have made the heavens and the stars; how all things also were numbered in Me before they were made, how by virtue of unchangeable principles your very hairs were numbered.” Did you think that Wisdom would say these things, and such as these? No. But first that. “That I am meek and lowly in heart.” Lo, see here what ye can comprehend, brethren; it is surely a little thing. We are making our way to great things, let us receive the little things, and we shall be great.
Would you comprehend the height of God? First comprehend the lowliness of God. Condescend to be humble for your own sake, seeing that God condescended to be humble for your sake too; for it was not for His own. Comprehend then the lowliness of Christ, learn to be humble, be loth to be proud. Confess your infirmity, lie patiently before the Physician; when you shall have comprehended His lowliness, you rise with Him; not as though He should rise Himself in that He is the Word; but you rather, that He may be more and more comprehended by you.
At first you understood falteringly and hesitatingly; afterwards you will understand more surely and more clearly. He does not increase, but you make progress, and He seems as it were to rise with you. So it is, brethren. Believe the commandments of God, and do them, and He will give you the strength of understanding. Do not put the last first, and, as it were, prefer knowledge to the commandments of God; lest ye be only the lower, and none the more firmly rooted. Consider a tree; first it strikes downwards, that it may grow up on high; fixes its root low in the ground, that it may extend its top to heaven.
Does it make an effort to grow except from humiliation? And would you without charity comprehend these transcendent matters, shoot toward the heaven without a root? This were a ruin, not a growing. With “Christ” then “dwelling in your hearts by faith, be ye rooted and grounded in charity, that you may be filled with all the fullness of God.”
Source: Sermons on Selected Lessons of the New Testament (New Advent)