Son 8:9    If she be a wall, we will build upon her a palace of silver: and if she be a door, we will inclose her with boards of cedar.

Son 8:10    I am a wall, and my breasts like towers: then was I in his eyes as one that found favour.

John Gill has a comment on these verses..

Song of Solomon 8:9

If she be a wall,…. Built upon a sure foundation; and firmly established in her faith on Christ, and love to him; and is constant therein, and stands as a wall against the attacks of enemies (b);

we will build upon her a palace of silver; though at first but as a side wall, yet should become a complete habitation, even a palace for Christ, the King of kings, and, being designed for so illustrious an inhabitant, should be a “silver” one, denoting its worth, value, and splendour; the builders of it are the church and her ministers; though Christ is the principal builder, Zec 6:12. Or, “a tower of silver” (c), signifying, that she should be well fortified, and be put into a posture of defence against her enemies: the Gentile church at first had but a very small appearance of a building, a foundation just laid, a side wall erected; but, in a short time, a noble structure, a stately tower, a silver palace, were built for God;

and if she be a door, we will enclose her with boards of cedar; if the door of the Gospel was opened among the Gentiles, it should be succeeded to the building a holy temple to the Lord; which should be not only ornamented, but so well fenced, that it should not be in the power of their enemies to deface and demolish it: or if the door of their hearts was opened, to receive Christ, and his glorious train of grace, they should be adorned and beautified with a larger measure of them; or if being come into a church state, and the door of it was set open to receive good men, and exclude bad men, this would be to their honour comfort and safety: or this phrase is expressive of the finishing of the building, the gate or door being set up; though it rather seems to intend the low and mean estate of the Gentile church at first, when there was but little appearance of a building, only a door set up; which afterwards grew up into a stately and magnificent palace, like that of Solomon’s, built of cedar boards of the wood of Lebanon; which may denote her fragrancy, perpetuity, and incorruptibleness.

(b) So Ajax is called the wall of the Grecians, Homer. Iliad. 6. v. 5. & 7. v. 211. (c) טירת כסף“propugnaculum argenteum”, Tigurine version; “arcem argenteam”, Mercerus; “castellum argenti”, Michaelis.

Song of Solomon 8:10

I am a wall,…. The words of the little sister, or Gentile church; either wishing she was what was supposed, and desiring to be in a well settled state, “O that I was a wall!” or as asserting (d) that she was in such a state, well walled; God was a wall of fire about her; salvation was appointed as walls and bulwarks to her; she was one of the two walls Christ was a cornerstone unto, and cemented together; and was a wall built up of lively stones, of true believers, built on Christ, the foundation; and established in the doctrine of grace; and constant and immovable in her love to Christ;

and my breasts like towers; round, plump, and high; signifying that she was now marriageable; and the time of her being presented as a chaste virgin to Christ, and of her open espousals to him, was now come: of ministers of the word, of the Scriptures, and of the ordinances of the Gospel, as signified by breasts; see Gill on Son 4:5; which may be said to be “like towers”: ministers of the word, because set for the defence of the Gospel; the Scriptures, because an armoury from whence saints are supplied with armour, to repel Satan’s temptations, refute errors, and defend truth; and the ordinances of the Gospel, because they stand firm and immovable against all the efforts of men to subvert and abolish them; and these are peculiar to the Gentile church, under the Gospel dispensation;

then was I in his eyes as one that found favour; from the time that the Gentile church became a wall, firmly built on Christ, and was formed into a church state, and had a settled ministry and Gospel ordinances, she became acceptable to Christ, and was admitted to near communion with him; and not only her person, but her services, met with a favourable acceptance from him; and these privileges and blessings were the fruit of his love, layout, and good will, he bore to her; which before was secret and hidden, but now her breasts being fashioned, her time was a time of love, of the open love of Christ to her, and of her espousals to him: and when, as the words may be rendered, she was “as one that found peace” (e); peace being made by the blood of Christ, and the partition wall broken down between Jew and Gentile, and they peaceably joined together in a Gospel church state; and when she enjoyed inward peace and tranquillity of mind, which is found in Christ, the word and ordinances; even all kind of prosperity, which peace, with the Hebrews, includes; every spiritual blessing, as reconciliation, justification, pardon, adoption, and eternal life, which are all the fruits and effects of divine favour, good will, grace, and love.

(d) “Hoc est, nolite dubitare ultrum murus sum”, Ambros. Enarrat. in Psal. cxviii. octon. 22. p. 1087. (e) שלום ειρηνην, Sept. “pacem”, Pagninus, Montanus, Marckius, Michaelis.