TT #12 · Parashas Chayei Sarah · Passuk 24:1
Avraham was now old, advanced in years, and Hashem had blessed Avraham in all things.
Torah Temimah points to Kiddushin 32b. E-Daf · Sefaria — Kiddushin 32b
TT lemma: ואברהם זקן.
Rabbi Chama son of Rabbi Chanina said: From the days of our ancestors the yeshiva never ceased among them. Avraham was an elder sitting in the yeshiva, as it is said “And Avraham was old.”
Custom (Bavli — zaken = one who acquired wisdom / yeshiva continuity)
The title “zaken” points to the acquisition of wisdom and to continuous Torah study. Avraham is portrayed as an elder who maintained a yeshiva; the same language marks the unbroken chain through the Patriarchs.