Or HaChaim on Genesis 22:20/אור החיים על בראשית כ״ב:כ׳

1 ויהי אחרי הדברים האלה, ויגד. After these events Abraham was told, etc.. The reason that the Torah recorded this whole paragraph as well as the words "after the events," something totally unrelated to what the Torah spoke about previously, is to tell us that now Rebeccah, Isaac's soul-mate, had been born. We have already explained why Rebeccah was born only at that point in time. Isaac, whose soul had originated in the female emanations, had not acquired a soul from the male emanations until after the עקדה, the binding on the altar. ובתואל ילד את רבקה, Bethuel fathered Rebeccah. This is the principal line of the whole paragraph. Why did the Torah have to bother to list all the other descendants of Nachor including those from his concubines? The Torah reminds us that ever since the spiritual poison of the original serpent permeated Adam, purity could no longer exist in isolation. The birth of even the most perfect human being is invariably accompanied by the birth of impure people who lie in wait for the pure. By telling us of the other descendants of Nachor, the Torah indirectly extols the virtue of Rebeccah, mother of all that is holy, who, despite the environment she grew up in, shone forth with her many virtues.