Flavius Josephus, Antiquities of the Jews
William Whiston, A.M., Ed.

[242] NOW when Abraham, the father of Isaac, had resolved to take Rebeka, who was grand-daughter to his brother Nahor, for a wife to his son Isaac, who was then about forty years old, he sent the ancientest of his servants to betroth her, after he had obliged him to give him the strongest assurances of his fidelity; which assurances were given after the manner following : - They put each other's hands under each other's thighs; then they called upon God as the witness of what was to be done. He also sent such presents to those that were there as were in esteem, on account that that they either rarely or never were seen in that country, The servant got thither not under a considerable time; for it requires much time to pass through Meopotamia, in which it is tedious traveling, both in the winter for the depth of the clay, and in summer for want of water; and, besides this, for the robberies there committed, which are not to be avoided by travelers but by caution beforehand. However, the servant came to Haran; and when he was in the suburbs, he met a considerable number of maidens going to the water; he therefore prayed to God that Rebeka might be found among them, or her whom Abraham sent him as his servant to espouse to his son, in case his will were that this marriage should be consummated, and that she might be made known to him by the sign, That while others denied him water to drink, she might give it him.