The wait for the promised son was long and hard. Abram looked forward to the fulfillment of the promise and we can see that his thoughts were firmly fixed on it. But for Sarai the wait appears to have been the most difficult. She, like most women, wanted a child of her own, and the social stigma of barrenness only added to her sorrow. In such a condition, Abram and Sarai made a fateful mistake for which we are still paying the price.
No doubt Sarai longed for the fulfillment of the promise, just as Abram did. But with no fulfillment in sight, Sarai began to consider other options. Was not Hagar able to bear children? Did not God promise Abram a son without limiting Himself to providing the son through Sarai? Perhaps the promised son would come through Hagar. Besides, if it was not God’s will, wouldn’t He simply close up Hagar’s womb? So goes human reasoning. Impatience produced the “solution” to the problem: Abram should go into Hagar and father children by her. That Abram offered no resistance to the idea seems to suggest that he, too, found the reasoning compelling.
This might strike us today as a very strange way to attempt to solve the problem. There is, however, more than meets the eye here—a cultural factor that would have provided a rationalization for Abram and Sarai. Dr. Eugene Merrill explains in his book Kingdom of Priests: A History of Old Testament Israel: “Certain peculiar actions of Abram and his wife in Genesis 15 and 16 require some attention to ancient Near Eastern custom and law, especially a few Hurrian practices attested in the Nuzi tablets [documents from northern Mesopotamia of the patriarchal age]…. [An] example is Sarai’s barrenness and the steps she took to ensure offspring in spite of it (Genesis 16:1-6 Genesis 16:1-6  Now Sarai Abram's wife bore him no children: and she had an handmaid, an Egyptian, whose name was Hagar.
 And Sarai said to Abram, Behold now, the LORD has restrained me from bearing: I pray you, go in to my maid; it may be that I may obtain children by her. And Abram listened to the voice of Sarai.
 And Sarai Abram's wife took Hagar her maid the Egyptian, after Abram had dwelled ten years in the land of Canaan, and gave her to her husband Abram to be his wife.
 And he went in to Hagar, and she conceived: and when she saw that she had conceived, her mistress was despised in her eyes.
 And Sarai said to Abram, My wrong be on you: I have given my maid into your bosom; and when she saw that she had conceived, I was despised in her eyes: the LORD judge between me and you.
 But Abram said to Sarai, Behold, your maid is in your hand; do to her as it pleases you. And when Sarai dealt hardly with her, she fled from her face.
American King James Version×). She simply offered her slave girl Hagar to Abram as a surrogate mother, and the child of that union, Ishmael, came to be regarded as the son of Abram and Sarai. This…is paralleled by Nuzi texts which describe the same remedy for a similar situation” (1987, pp. 38-39).
Yet Ishmael, despite cultural precedent, was clearly not Sarai’s son—neither in her own eyes nor in the eyes of God—and trouble and heartache ensued within the family. Furthermore, Ishmael would ultimately become the father of many of the Arab peoples so that, even today, we still live with the tragic results of Sarai’s solution—i.e., major facets of the perpetual Middle East conflict.
The lesson ought to be obvious. What would have happened if Sarai and Abram had simply waited for God to provide the solution? Perhaps generations of strife could have been avoided. The geopolitical scene today might be very different, with the ever-present threat of war much diminished. We must learn to live with what God gives us, trusting that if He has made a promise He will fulfill it at just the right time and in just the right way. Man cannot bring about the fulfillment of God’s promises on his own. To attempt to do so is presumptuous and inevitably leads to misery. But to patiently wait for God to act, knowing that He cannot lie, builds faith and character, and avoids what could be generations of strife.
Supplementary Reading: “Profiles of Faith: Sarah--A Story of Virtue,” The Good News, Mar.–Apr. 1996