27 But they of whose iniquities this Psalm speaks, when they had entered into that temporal land of promise, “destroyed not the heathen, which the Lord commanded them”; “but were mingled among the heathen, and learned their works”. “Insomuch that they worshipped their idols, which became to them an offense”. Their not destroying them, but mingling with them, became to them an offense.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)