Israel’s 12 tribes, of which Gad was one, were named for Jacob’s children (or grandchildren, in the cases of Ephraim and Manasseh). “Israel” was God’s name for Jacob (Genesis 32:22-30); therefore, the phrase “children of Israel” is a way of referring to Jacob’s descendants. Jacob’s son Gad was born in Paddan Aram to Jacob’s first wife’s maidservant, Zilpah (Genesis 35:26). When Jacob blessed his 12 sons, he said, “Gad will be attacked by a band of raiders, but he will attack them at their heels” (Genesis 49:19). Later, Moses blessed the tribe of Gad, saying, "Blessed is he who enlarges Gad's domain! Gad lives there like a lion, tearing at arm or head. He chose the best land for himself; the leader's portion was kept for him. When the heads of the people assembled, he carried out the LORD's righteous will, and his judgments concerning Israel" (Deuteronomy 33:20-21).
The tribe of Gad was one of three (Reuben and the half-tribe of Manasseh were the others) to fight for and be awarded lands east of the Jordan River, the gateway to the Promised Land (Joshua 12:6; 13:8-13). When Gad and the other tribes first requested this land outside of the Promised Land, Moses warned that their actions could discourage the others from taking the land God had given, much like the ten spies' fearful report forty years previously. The Reubenites and Gadites said, “We would like to build pens here for our livestock and cities for our women and children. But we will arm ourselves for battle and go ahead of the Israelites until we have brought them to their place. Meanwhile our women and children will live in fortified cities, for protection from the inhabitants of the land. We will not return to our homes until each of the Israelites has received their inheritance. We will not receive any inheritance with them on the other side of the Jordan, because our inheritance has come to us on the east side of the Jordan” (Numbers 32:16–19). Moses agreed: "Then Moses said to them, 'If you will do this—if you will arm yourselves before the LORD for battle and if all of you who are armed cross over the Jordan before the LORD until he has driven his enemies out before him—then when the land is subdued before the LORD, you may return and be free from your obligation to the LORD and to Israel. And this land will be your possession before the LORD. But if you fail to do this, you will be sinning against the LORD; and you may be sure that your sin will find you out" (Numbers 32:20–23).
The tribes were faithful to their commitment (Numbers 32:25; Joshua 22:1–6). When they returned to their own land they built an altar. The other Israelites came out against them, thinking they were rebelling against the Lord. But the tribes of Gad, Reuben, and the half-tribe of Manasseh called on the Lord saying He knew their motives and if they had acted in rebellion or disobedience they should not be spared. In fact, they had built the altar not to make sacrifices but "to be a witness between us and you and the generations that follow, that we will worship the LORD at his sanctuary with our burnt offerings, sacrifices and fellowship offerings. Then in the future your descendants will not be able to say to ours, 'You have no share in the LORD'" (Joshua 22:27). Though the tribes had settled on the other side of the Jordan, they were still very much committed to worshipping God. They were still part of Israel and wanted to prevent the Jordan River, a significant geographical divide between Gad and the majority of the other tribes, from spiritually dividing God’s people then or in future generations (Joshua 22:10-34). “And the Reubenites and Gadites gave the altar this name: A Witness Between Us—that the LORD is God” (Joshua 22:34).
Gad, along with all the other northern tribes of Israel, was sent into exile in 722 BC (2 Kings 15:29 – 17:41). Gad’s specific circumstances, seemingly triggered by the half-tribe of Manasseh’s unfaithfulness to God, are described in 1 Chronicles 5:11-26.
We see in the tribe of Gad fidelity to God and to their commitments to others. Perhaps the most important lesson we learn from Gad (and all the other tribes) is to recognize the need for complete faith and trust in God. God commanded Moses to remind the Israelites to “carefully follow the terms of this covenant, so that you may prosper in everything you do” (Deuteronomy 29:9). “Make sure there is no man or woman, clan or tribe among you today whose heart turns away from the Lord our God to go and worship the gods of those nations; make sure there is no root among you that produces such bitter poison” (Deuteronomy 29:18).