Until Abraham there was no aging… Abraham prayed for mercy, and aging came into the world, as it is said: “And Abraham was old, advanced in days.”
On the daf / in context: Before Avraham people looked alike across generations; Avraham asked for the distinguishing mark of old age so that father and son could be told apart.
Type of Learning
Custom (Bavli — introduction of visible old age)
What Is Learned
Visible signs of age began with Avraham’s request, so that the generations could be distinguished and proper honor given according to seniority.