English: From here [we learn] that one who swears must hold a sacred object in his hand.
On the daf / in context: The requirement that a person taking an oath grasp a sacred object (Sefer Torah, tefillin, etc.) is derived from Avraham’s instruction to Eliezer to place his hand under the thigh (the site of the milah, the sacred covenant). Later authorities discuss whether tefillin alone suffice for a scholar.
Type of Learning
Custom (Bavli — holding a sacred object for an oath)
What Is Learned
An oath requires the swearer to grasp a sacred object. Avraham’s demand that Eliezer place his hand under the thigh (the covenant of milah) is the Torah’s paradigm for this practice.