Genesis 25:26
And after that came his brother out, and his hand took hold on Esau’s heel; and his name was called Jacob: and Isaac was threescore years old when she bare them. And after that came his brother out, and his hand took hold on Esau’s heel; and his name was called Jacob: and Isaac was threescore years old when she bare them.
The birth noted in Genesis 25:26 falls within overlapping lifetimes that still linked back to Adam, for Abraham lived until the twins were fifteen years old and Isaac lived until they were one hundred and twenty. Through that overlap Jacob, the father of the tribes of Israel, personally received from Abraham and Isaac the knowledge of what God had taught Adam, which had been handed down through Methuselah and Shem. Before the birth God gave Rebekah a divine intimation that the birthright should fall to Jacob, and Rebekah told Jacob of it. That promise filled Jacob with unspeakable desire for the privileges of the spiritual birthright, not for his father's wealth.
What he longed for was to commune with God as righteous Abraham did, to offer the sacrifice of atonement for his family, to be the progenitor of the chosen people and of the promised Messiah, and to inherit the immortal possessions embraced in the blessings of the covenant. He listened with secret longing to all his father told about the spiritual birthright, treasured what he learned from his mother, and thought on it day and night until it became the absorbing interest of his life. Although he esteemed eternal blessings above temporal ones, he had no experimental knowledge of the God he revered and his heart had not been renewed by divine grace. He believed the promise concerning himself could not be fulfilled so long as Esau retained the rights of the firstborn, so he constantly studied to devise some way to secure the blessing that his brother held lightly but that was precious to himself.