"And the child grew and was weaned." That he was weaned from the evil inclination to the good inclination. And the Rabbis said: That he was weaned from his milk.
Isaac Weaned From the Evil Inclination to the Good
Yalkut Shimoni on Torah 94:1
וַיִּגְדַּל הַיֶלֶד וַיִּגָּמַל, שֶׁנִּגְמַל מִיֵּצֶר הָרָע לְיֵצֶר טוֹב וְרַבָּנָן אַמְרִי שֶׁנִּגְמַל מֵחֲלָבוֹ.