Another interpretation: "after these things" means Isaac and Ishmael were disputing with one another. This one said, "I am greater than you, for I was circumcised at eight days." Ishmael said, "I am more beloved, because it was in my power to protest and I did not protest." [He had been circumcised at thirteen years of age and could have resisted.] At that hour Isaac said, "Would that the Holy One, blessed be He, reveal Himself to me and tell me to cut off one of my limbs, and I would not hold back." The Holy One, blessed be He, said to him: On the condition that you would offer up yourself and not hold back.
Isaac and Ishmael Dispute Over Circumcision Before the Binding
Yalkut Shimoni on Torah 95:9
דָּבָר אַחֵר, אַחַר הַדְּבָרִים הָאֵלֶה יִצְחָק וְיִשְׁמָעֵאל הָיוּ מִדַּיְּנִין זֶה עִם זֶה. זֶה אוֹמֵר, אֲנִי גָּדוֹל מִמְּךָ שֶׁמַּלְתִּי לִשְׁמוֹנָה יָמִים אָמַר יִשְׁמָעֵאל, אֲנִי חָבִיב, לָמָּה שֶׁהָיָה בְּיָדִי לִמְחוֹת וְלֹא מָחִיתִי. בְּאוֹתָה שָׁעָה אָמַר יִצְחָק, הַלְּוַאי יִגָּלֶה עָלַי הַקָּדוֹשׁ בָּרוּךְ הוּא, וְיֹאמַר לִי שֶׁאֶחְתֹּךְ לִי אֶחָד מֵאֵבָרַי, וְלֹא אֲעַכֵּב. אָמַר לוֹ הַקָּדוֹשׁ בָּרוּךְ הוּא, עַל מְנַת שֶׁתַּקְרִיב עַצְמְךָ וְלֹא תְּעַכֵּב.