Genesis 24:8

Thou shalt be clear. In view of the sacred and binding nature of his oath, Eliezer felt justifiable concern as to his responsibility in case no woman would return with him to Canaan. Abraham assured Eliezer that God, who had led thus far, could be counted on not to desert him now. Eliezer could set out confident in the successful conclusion of his mission. But if for any reason the contrary should prove true, he was to consider himself free from further obligation with respect to the oath, except that under no circumstance was Isaac to be permitted to go to Mesopotamia to seek a wife. Abraham no doubt feared that Isaac might be tempted to remain in Mesopotamia, and so thwart the divine purpose.