(Chapter 24, Verse 9) And the servant put his hand under the thigh of his master Abraham and swore to him concerning this matter. The Hebrews say that he swore at his consecration, that is, at his circumcision. But we say that he swore by the seed of Abraham, that is, by Christ, who was to be born from him, according to the Gospel of Matthew, which says: The book of the genealogy of Jesus Christ, the son of David, the son of Abraham (Matthew 1:1).
[AD 420] Jerome on Genesis 24:9