"And the souls that they had made in Haran" (Genesis 12:5). It is a received tradition that at that time Abraham was fifty-two years old. And when you examine it, from "and the souls" until the giving of the Torah there were four hundred and forty-eight [448] years.
Abraham Was Fifty-Two When He Left Haran
Yalkut Shimoni on Torah 66:5
וְאֶת הַנֶּפֶשׁ אֲשֶׁר עָשׂוּ בְחָרָן. גְּמִירִי: בְּהַהִיא שַׁעֲתָא אַבְרָהָם בַּר חַמְשִׁין וְתַרְתֵּין שְׁנִין. וְכִי מְעַיְּנַת, מִ'וְאֶת הַנֶּפֶשׁ' עַד מַתַּן תּוֹרָה תמ"ח הֲווֹ.