Now therefore you are cursed, and some of you shall never be anything but servants, cutters of wood and drawers of water for the house of my God.
Joshua 9:23 ESV

Joshua and the elders made the Gibeonites to be perpetual servants of God. This was punishment for deceiving Israel, but also ensured they would be constantly exposed to the worship and teaching of God. He also gave their capital city, Gibeon, to the Levites, probably for the same purpose.