Completing the monumental building projects in Jerusalem required settling accounts and closing massive financial debts. The close alliance between Solomon and Hiram, the king of Tyre, finally reached the stage of final payment, resulting in an exchange of precious raw materials for territorial compensation.
Throughout the long years of constructing the Temple and the royal palace, Hiram bore a heavy burden to sustain Solomon, supplying all the necessary wood and gold for these grand endeavors [מצודת דוד, ביאור שטיינזלץ]. The primary approach among commentators is that Hiram's involvement was defined by carrying this immense load and sharing the physical weight of the work [רש״י, מצודת ציון]. A different perspective suggests that his assistance functioned as a royal gift, or that Hiram actively elevated and magnified Solomon by willingly taking on the role of a servant to ensure the construction was completed [רלב״ג].
When the years of construction came to a close, the time arrived to settle the debt. As a final payment and reward for his extensive help, Solomon gave Hiram twenty cities. This territorial transfer was in addition to the regular, ongoing shipments of wheat and oil that had already been provided to him up to that point [מצודת דוד, ביאור שטיינזלץ].
Handing over twenty cities to a foreign ruler raises significant questions. It reveals that despite his legendary wealth, Solomon could not finance the overwhelming expenses of his projects solely from his own treasuries. However, this transfer was not a complete annexation of the cities and their inhabitants into foreign territory. Instead, the cities were merely mortgaged to Hiram, granting him the right to collect agricultural taxes from their crop yields [ביאור שטיינזלץ]. Furthermore, a deeper issue arises regarding the transfer of territory from the Land of Israel, as a king is not expected to diminish the borders of the land. This difficulty is resolved by parallel historical records indicating a mutual exchange. In return for these twenty cities, Hiram gave other towns to Solomon, who then settled Israelites in those newly acquired areas [רלב״ג].