genesis 21:13 God promised Abraham that Ishmael's descendants will create a great nation. My atheist friend argued that if the Bible is true then how come there's no great nation from Ishmael's descendants. How can I prove him wrong by showing proof?
The bible also says Abraham's descendants will be as numerous as the stars...there are over 100 billion stars just in our own galaxy, and hundreds of billions of galaxies -- and nowhere near that many descendants of "Abraham" (if such a person ever existed anyway). That one fails, too. Like all the others.
Being a great nation does always not mean being a world power such as Egypt or Rome.
As a nomadic inhabitant of the Paran Wilderness, Ishmael fulfilled the prophecy that said of him: “He will become a zebra of a man. His hand will be against everyone, and the hand of everyone will be against him; and before the face of all his brothers he will tabernacle.” (Ge 21:17-21; 16:12) Hagar found an Egyptian wife for her son, and he in time fathered 12 sons, chieftains and family heads of the promised “great nation” of Ishmaelites. Ishmael also had at least one daughter, Mahalath, who married Esau.—Ge 17:20; 21:21; 25:13-16; 28:9
The name Ituraea is thought to derive from Ishmael’s son Jetur, whose descendants residing E of the Jordan were defeated by the Israelites. (Ge 25:15,*16; 1Ch 1:31; 5:18-23) Toward the close of the second century*B.C.E., the Maccabean king Aristobulus I successfully warred against Ituraea and added much of its territory to Judea. To remain in the country, the inhabitants of Ituraea had to submit to circumcision and obey Jewish law. (Jewish Antiquities, XIII, 318 [xi, 3]) Later, Ituraea was one of the territories comprising the tetrarchy of Philip, inherited from his father Herod the Great.—Lu 3:1.