Scripture records how Abraham distinguished between Isaac and his other children:
And Abraham gave all that he had unto Isaac. 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. (Genesis 25:5-6)
To help clarify the rather vague reference to "the east country," The Dake Annotated Reference Bible offers the following explanation, on page 20 of the Old Testament:
This refers to the east of Canaan where Abraham settled. Just how far east isn't stated, but we know that the Midianites, Ishmaelites, Moabites, Edomites, and others settled east of Canaan proper. The terms "people," "children," and "men of the east" are used of Abraham's own people in Mesopotamia (29:1); of various unnamed people who cooperated with the Midianites against Israel (Judg. 6:3, 33; 7:12; 8:10); of Job and his kindred east of Arabia (Job 1:3); of Babylon and other eastern lands (2 Ki. 17:24; Isa. 2:6; Ezek. 25:4, 10; Mt. 2:1); of Persia (Isa. 41:2; 46:11); of unidentified nations east of Syria, Babylon, and Persia who will fight Antichrist (Dan. 11:44); and of other people further east who will cooperate with Antichrist at Armageddon (Rev. 16:12).