Fausset's Bible Dictionary 
Their safety was covenanted by Israel (Joshua 9), even though obtained by a deceit, their ambassadors having taken old sacks and mended wineskins (the tear being tied up like a bag) and old mended sandals ("clouted," i.e. mended coarsely); but they were made "hewers of wood and drawers of water." Israel's error was in making the treaty without inquiring of the Lord; a warning to the church of all ages against the dissimulation of the world, which seeks admission and union with the kingdom of God without real conversion, faith, and sanctification, when it suits its own carnal advantage. Saul in his zeal for Israel where God sanctioned it not, though wanting in zeal against Israel's foe Amalek ( 1 Samuel 15:18-20) where God commanded it, sought to slay them, probably (2 Samuel 21) in the dark closing period of his reign seeking to atone for his deficiency as to Amalek and to win the divine favor and popularity with his people by this mis-timed and misplaced zeal.
God remembers the sins of the fathers upon the children, and vindicates His righteousness as Ruler of the nations by making an entail of curse go down from one generation to another for the unexpiated guilt of bloodshed and violation of covenants. The three years' famine, the Lord's answer when consulted as to the cause, that it was "for Saul and his bloody house because he slew the Gibeonites," and after the execution of Saul's seven (seven, the sacred number, denotes the performance of a work of God) sons "the Lord being entreated for the hind," prove that David did not contrive or eagerly fall in with this device for ridding himself of the remainder of Saul's royal line. Nay, he showed by the honorable burial he gave their remains, and by sparing Mephibosheth, that he entertained no such feeling, nor had he by this time anything to fear from Saul's family.
The whole matter was divinely ordered to teach solemn moral lessons of God's government to the king and the nation ( Exodus 20:5; Exodus 34:7; Leviticus 26:34-40; Numbers 14:18-34, especially Numbers 35:33, "blood it defileth the land, and the land cannot be cleansed of the blood that is shed therein but by the blood of him that shed it"; Isaiah 14:20-21; Isaiah 65:6-7; Jeremiah 2:9; Jeremiah 32:18). The "water dropping upon them (the hanged or crucified seven) out of heaven" marked the cessation of the heaven sent drought and the point of time when the bodies might be taken down from the stakes and buried. Ordinarily bodies were taken down for burial before night ( Deuteronomy 21:22-23); but in this case guilt rested on the whole land, and therefore the expiatory sacrifice was to remain exposed to birds of prey (the greatest ignominy, 1 Samuel 17:44) before Jehovah, until the cessation of the drought showed that His wrath was appeased.
Morrish Bible Dictionary 
The people of Gibeon and perhaps of the three confederate cities Chephirah, Beeroth, and Kirjath-jearim. Joshua 9:17 . They were Hivites, and 'mighty' men. Having deceived Joshua into making a treaty with them, they were made hewers of wood and drawers of water for the house of God. Joshua 9:23 . Saul, upon an occasion not recorded, had slain some of the Gibeonites, and it apparently had been passed over and forgotten; but God could not allow the oath of His people to be violated; He therefore brought a famine on the land. On David inquiring of the Lord, it was revealed that the famine was because of the slaying of the Gibeonites. They were appealed to, and reparation offered them. They claimed that as it was Saul who had sought to destroy them from remaining in any of the coasts of Israel, seven of his descendants should be given to them. These they hanged in the hill before the Lord, and God was entreated for the land. 2 Samuel 21:1-14 . In this passage the Gibeonites are called 'Amorites,' a common designation of the Canaanites, which does not clash with their being called Hivites in Joshua 9:7 . Ismaiah, one of David's thirty mighty men, was a Gibeonite. 1 Chronicles 12:4 . Some of them returned from exile and helped to build the wall of Jerusalem. Nehemiah 3:7; Nehemiah 7:25 .
Hawker's Poor Man's Concordance And Dictionary 
International Standard Bible Encyclopedia 
gib´ē̇ - un - ı̄ts . Inhabitants of Gibeon (which see).