English: When Sarah gave birth to Yitzchak, people were murmuring and saying, “Can Avraham, a hundred years old, beget a child?” Immediately the features of Yitzchak’s face were transformed and became like Avraham’s; then all opened and said, “Avraham begot Yitzchak.”
On the daf / in context: The doubled phrasing of the verse is read as the public affirmation that silenced the rumor attributing the child to Avimelech.
Type of Learning
Custom (Bavli — resemblance proves paternity)
What Is Learned
Heaven caused Yitzchak’s face to resemble Avraham’s so that all would acknowledge “Avraham begot Yitzchak” and the rumor of foreign paternity would cease.