Dora Bas Rivka Silver O'H
Avraham was advanced in years and Sarah had passed on, leaving the family without a lady of the house. All of this underscored that it was well past time Yitzchak got married. Avraham appointed his servant Eliezer to find a bride for Yitzchak. He made Eliezer swear that he would not take a wife for Yitzchak from the Canaanite nations; rather, Eliezer was to travel to Avraham's birthplace and acquire a wife from his own kin. Eliezer was concerned that no one would be willing to come back with him; in that case, Avraham said, Eliezer would be released from his vow. But most importantly, Eliezer was not to bring Yitzchak back to Mesopotamia; G-d had taken Avraham from there to Israel, which He promised to Yitzchak as an inheritance.
Eliezer swore this oath by placing his hand on the place of Avraham's circumcision. This act was tantamount to someone placing their hand on a Bible. It's just that, since the Torah had not yet been given, this was the only tangible sign of the covenant with G-d.