Thought from Today's Old Testament Passage:
When the time drew near that Israel must die, he called his son Joseph and said to him, "Now if I have found favor in your sight, please put your hand under my thigh, and deal kindly and truly with me. Please do not bury me in Egypt,…" (Gen. 47:29)
The "thigh" (yarekh) or "loins" is here indeed regarded as "the seat of the procreative powers" (B D B), and by metonomy it takes into consideration all the descendants of one.… Consequently, this form of oath has particular regard to the descendants and is taken in reference to them. But we cannot stop short with this correct statement. For when we consider how eagerly believers from the time of Adam looked forward to a Savior that was to be born, and also how Abraham (12:3) knew and believed that from his own line such a Savior was to follow, we cannot but accept the orthodox view held by church fathers from days of old that this oath was administered in view of the Savior to come from Abraham's line. The whole course of procedure builds upon this prominent fact. …
Jacob believed God's promises in reference to Israel, the land of Canaan, and the blessing of all the nations of the world through the Savior to come. His deepest hopes were tied up with these promises of the Word of God.
H. C. Leupold, Exposition of Genesis, Vol. II, (Grand Rapids, MI: Baker Book House, 1942), pp. 659, 1140