EXEGESIS -- ISAIAS.
"The Mother of the Lord is the rod, simple, pure, sincere, without any germ extrinsically cleaving to it; and, after the likeness of God, of itself alone fruitful. The Flower of the rod is Christ, who says, I am the flower of the field, and the lily of the valleys;* who also in another place is set forth as the stone cut out from the mountain without hands;+ whereby the prophet signifies, that Virgin He is to be born of a Virgin."++
S. Cyril of Jerusalem shows that Mary is both the rod of Aaron and of Jesse;** as do also many other Fathers.
"Blossoming rod of Aaron.|| For truly thou wert the rod, and thy Son the flower; since from the root of David and Solomon budded forth Christ, our Creator, Almighty God and Lord, the alone Most High. Of Him who is God and Man art thou Mother, Virgin before birth, Virgin in birth, and Virgin after birth."***
S. Hippolytus brings forward the prophecy of Jacob+++ and compares it with this passage of Isaias saying:--
"The prophet called a lion's whelp Him who of Juda and David was made according to the flesh -- not, indeed, made of David's seed,||| but conceived of the Holy Ghost, and come forth of a holy germ from the earth. And this Isaias thus expresses: There shall come forth a rod out of the root of Jesse, and from it a flower shall rise up. That which Isaias speaks of as a flower, Jacob called a shoot. For first it put forth buds, and then it flowered in the world."++++
"Behold the Lord will ascend upon a swift cloud, and will enter into Egypt, and the idols of Egypt shall be moved at His presence, and the heart of Egypt shall melt in the midst thereof." -- xix. 1.
||| But S. Paul says that He was made of the Seed of David according to the flesh (Rom. i. 3); that is, inasmuch as He received His assumed human nature from David by the Virgin Mary: but He was not made of the seed of David, if regard be had to the way of His conception, viz., by no seed of earthly father.
++++ S. Hippolytus, Demonstrat. de Christo et Antichristo SS. viii., Galland T. ii., p. 420. See also S. Justin M., Apol. ii. 32. Tryph. 86, 87; Tertullian, De carn. Christi. 21; Novatian, De Trin. c. 9; Methodius, De Sim. et Anna 10; Lactantius, Div. Inst. L. iv. c. 13; S. Ambrose, De benedict. patriarch. c. iv. 19; S. Augustine, Serm. de Symb. ad Catech. iv. n. 4; Chrysippus, Orat. de Virg. laud.; Hesychius, De Virg. laud.; S. Maximus, Hom. V. de Pasch; Theodoret, Commentar. in Is. xi.; S. Leo M. Serm iv. In Dom. Nativ.; S. Gregory the Great, Comment. in 1 Reg. c. 1, and supra, p. 104.