Jamieson, Fausset and Brown on Genesis 24:2

2. said unto his eldest servant--Abraham being too old, and as the heir of the promise not being at liberty to make even a temporary visit to his native land, was obliged to intrust this delicate mission to Eliezer, whom, although putting entire confidence in him, he on this occasion bound by a solemn oath. A pastoral chief in the present day would follow the same course if he could not go himself.