Another interpretation of "After these things" (Genesis 22:20): after the troubling thoughts about the matters that had occurred there. Who was troubled by such thoughts? Abraham was troubled. He said: "Had Isaac died on Mount Moriah, he would have died without children. Now that a miracle was done for him, I will take a wife for him from the daughters of Aner, Eshkol, and Mamre, who are righteous women, even though they are not of distinguished lineage; for what does lineage matter to me?" The Holy One, blessed be He, said to him: "There is no need. The mate of your son Isaac has already been born, as it is said, 'Behold, Milcah also has borne children' (Genesis 22:20)." What is the meaning of "also she"? Just as this one [Sarah] had children of the mistress numbering eight and children of the concubine numbering four, so too this one [Milcah, in her household] had children of the mistress numbering eight and children of the concubine numbering four.
Abraham Worries Over a Wife for Isaac After the Binding
Yalkut Shimoni on Torah 102:4
דָּבָר אַחֵר, אַחֲרֵי הַדְּבָרִים אַחַר הִרְהוּרֵי דְּבָרִים שֶׁהָיוּ שָׁם, מִי הִרְהֵר, אַבְרָהָם הִרְהֵר. אָמַר אִלּוּ מֵת יִצְחָק בְּהַר הַמּוֹרִיָּה, לֹא הָיָה מֵת בְּלֹא בָּנִים, עַכְשָׁיו שֶׁנַּעֲשָׂה לוֹ נֵס אֲשִׂיאֶנוּ מִבְּנוֹת עֵנָר אֶשְׁכֹּל וּמַמְרֵא, שֶׁהֵן צִדְקָנִיּוֹת, אַף עַל פִּי שֶׁאֵינָן מְיוּחָסוֹת, דְּמַה אִכְפַּת לִי בְּיוֹחֲסִין אָמַר לוֹ הַקָּדוֹשׁ בָּרוּךְ הוּא, אֵינוֹ צָרִיךְ, כְּבָר נוֹלְדָה בַּת זוּגוֹ שֶׁל יִצְחָק בִּנְךָ, שֶׁנֶּאֱמַר, הִנֵּה יָלְדָה מִלְכָּה גַּם הִיא, מַהוּ גַם הִיא, מַה זוֹ בְּנֵי גְּבִירָה שְׁמוֹנָה, וּבְנֵי פִּילַגְשִׁים אַרְבָּעָה אַף זוֹ בְּנֵי גְּבִירָה שְׁמוֹנָה, וּבְנֵי פִּילַגְשִׁים אַרְבָּעָה.