Genesis 30:14
And Reuben went in the days of wheat harvest, and found mandrakes in the field, and brought them unto his mother Leah. Then Rachel said to Leah, Give me, I pray thee, of thy son’s mandrakes. And Reuben went in the days of wheat harvest, and found mandrakes in the field, and brought them unto his mother Leah. Then Rachel said to Leah, Give me, I pray thee, of thy son’s mandrakes.
Genesis 30:14 belongs to the account of Jacob's years of service to Laban in Haran, including his marriages to Leah and Rachel, the sons born to him there, and God's prospering him in flocks and herds despite Laban's efforts to deprive him of his due. It falls within the account of Jacob's trials and victories that led to his change of heart and his place among the Israel of God. In this setting Jacob was deceived in his marriage just as he had deceived his father, yet God cared for him despite his selfishness and unfaithfulness.
The verse belongs to a story of troubled and unsatisfactory experiences in which selfish scheming brought suffering, the one who overreached others was himself overreached, and God's providence brings retribution even when it seems slow. It shows part of the great unhappiness that polygamy brought into Jacob's family, and belongs with the record of Abraham, Jacob, and David as proof that wherever polygamy entered it caused very great unhappiness. Polygamy was never anything but evil and wrong, tolerated by Moses because of hardness of heart, while the true standard is the original order of marriage in Eden. The verse is among the examples of patriarchal family arrangements that involved violations of the marriage institution, and such violations do not make marriage itself less sacred.