2 Samuel 5:7 (BSB)

Nevertheless, David captured the fortress of Zion (that is, the City of David).

From 2 Samuel 5. Also in the ESV.

Commentary on 2 Samuel 5:7

• Matthew Henry (Presbyterian), Matthew Henry's Complete Commentary on 2 Samuel 5:6-10: If Salem, the place of which Melchizedec was king, was Jerusalem (as seems probable from Psa 76:2), it was famous in Abraham's time. Joshua, in his time, found it the chief city of the south part of Canaan, Jos 10:1-3. It fell to Benjamin's lot (Jos 18:28), but joined close to Judah's, Jos 15:8.
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on 2 Samuel 5:7: Nevertheless, David took the strong hold of Zion,.... A fortress without the city, and separate from it, and which was very strong; and the taking it might facilitate the taking of the city, which yet as appears by what follows, was very difficult to do: the same is the city of David; it was afterwards so called, where he built an house, and dwelt.
• Jamieson-Fausset-Brown (Reformed), Commentary Critical and Explanatory on the Whole Bible on 2 Samuel 5:7: the stronghold of Zion--Whether Zion be the southwestern hill commonly so-called, or the peak now level on the north of the temple mount, it is the towering height which catches the eye from every quarter--"the hill fort," "the rocky hold" of Jerusalem.
• Keil & Delitzsch (Lutheran), Biblical Commentary on the Old Testament on 2 Samuel 5:7-8: 2Sa 5:7-8 However, David took the citadel Zion, i.e., “the city of David.” This explanatory remark anticipates the course of events, as David did not give this name to the conquered citadel, until he had chosen it as his residence and capital (vid., 2Sa 5:9). ציּון (Sion), from ציה, to be dry: the dry or arid mountain or hill.