Avraham accepted Efron’s terms. Avraham paid out to Efron the money that he had named in the hearing of the children of Ches—four hundred shekels of silver at the going merchants’ rate.
Rabbi Chanina said: Every unspecified “silver” in the Torah is a sela, except for the silver of Efron…
On the daf / in context: Bekhoros 50a establishes the default value of biblical shekel as a sela, with Efron’s payment as the exception requiring commercial-weight coins.
Type of Learning
Custom (Bavli — value of biblical shekel; exception of Efron)
What Is Learned
Unspecified monetary amounts in the Torah are ordinary selas; Efron’s four hundred were the heavier commercial standard.