Genesis 25:6

But unto the sons of the concubines which Abraham had Abraham gave gifts, and sent them away from Isaac, his son, while he yet lived, eastward, unto the east country. Although neither Keturah nor even Hagar were concubines in the later sense of the term, yet, in comparison with Sarah, the mistress and mother by special divine interposition, they were of secondary rank. Their children, therefore, could not claim an equal division of the property with Isaac, the heir of the promise, whose inheritance the land of Canaan was to be. Abraham simply established Ishmael and all the sons of Keturah with enough property in small herds and flocks, together with the necessary servants, that they had their maintenance. They moved into the country toward the southeast and east, and there grew up into tribes. Among these descendants of Abraham the knowledge of the true God was found for a long time, their spiritual inheritance thus proving of greater value than the temporal gifts.