Introducing Sarai's physical condition so early in the biblical narrative serves as much more than a simple biographical detail. It lays the essential groundwork for a forthcoming chain of trials, divine promises, and miracles. Her condition represents a complete stoppage of natural physical and reproductive forces [רש ר הירש].
The narrative seemingly repeats itself when describing her childless state. One approach suggests this is simply a sequential explanation, meaning she was considered barren merely because she had not yet given birth by that point in her life [שד״ל]. However, the primary approach among commentators is that this repetition emphasizes an absolute medical and physiological reality. Unlike other women who might experience delays but eventually give birth, Sarai possessed no natural capacity to ever bear a child [רבנו בחיי]. According to ancient tradition, she completely lacked the internal organs required for pregnancy [אור החיים, תורה תמימה, דעת זקנים]. This reality stands in sharp contrast to Nahor's wife, Milcah. While Milcah also experienced years of delay due to temporary illness or miscarriages, she was not naturally barren and eventually established a complete dynasty, whereas Sarai had no child at all [רד״ק, מלבי״ם, קאסוטו, ביאור שטיינזלץ].
Highlighting the absolute nature of Sarai's condition serves several profound purposes in the unfolding story. First, it magnifies the future miracle of Isaac's birth. It was not merely a case of an elderly woman conceiving, but a miracle within a miracle. A woman who had been completely incapable of having children since her youth gives birth in defiance of all natural laws [רד״ק, ביאור יש״ר, תורה תמימה]. Second, it underscores the extraordinary strength of Abraham's faith and dedication. When God promises to make him a great nation, Abraham believes Him completely, despite knowing clearly that his wife is barren and they have no natural chance of starting a family [קאסוטו, שד״ל]. Furthermore, when Abraham is commanded to leave his homeland, he leaves behind all his wealth and family inheritance. The fact that he does not even have a son to inherit his legacy deeply amplifies the magnitude of his sacrifice as he blindly follows God's command [בכור שור].
Finally, the barrenness itself acts as a hidden motivation for their journey to the land of Canaan. Their departure was rooted in the hope that changing their location might change their fortune, or that the spiritual merit of the holy land would finally allow them to build a family [שד״ל, רבנו בחיי]. Within this seemingly negative reality, some commentators find a subtle hint of a future promise. The extra emphasis on her having no child implies a specific limitation of time and place. She has no child right now in Ur of the Chaldeans, but in the future, upon reaching the land of Canaan, she will [רד״ק, פענח רזא, חזקוני, דעת זקנים].