Your neck is like the tower of David built for an armory, on which there hang a thousand shields, all shields of mighty men.
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Aquinas Study Bible
tower of David: Whenever proper names are mentioned in Scripture, one takes account either of the meaning of the name, or the office to which the person is assigned, or of the significance of something the person has accomplished. Here David being king points to Christ the King. (Honorius of Autun)
neck: God's people are tall and nicely uplifted, and in that way it is similar to a tower. (Nicholas of Lyra)
thousand bucklers: for innumerable rational defenses have been bestowed upon the Church so that by their means she may defend herself against adversaries. (Honorius of Autun)
Bulwarks. Hebrew Thalpiyoth, "at the height of the defiles "probably in Libanus, when David conquered Syria. Thalassar, Thelmela, were such "heights. "Bucklers, to be used in case of need, or for ornament. Thus the neck of the spouse was adorned with chains and pearls. The Church is this tower, the pillar of truth, 1 Timothy iii., and Matthew xvi. 18. Apostles and prelates are her bucklers.