In Parshat Toldot (Genesis 27:1-28:9) we read of one of the most a dramatic moments in the Torah: Rebeka, overhearing a conversation between Isaac and his eldest son Esau orders Jacob to deceive his poor sighted father, dress up as Esau and receive Isaac's final blessing:
"And Rebeka heard when Isaac spake to Esau his son. And Esau went to the field to hunt for venison, and to bring it. And Rebekah spake unto Jacob her son, saying, Behold, I heard thy father speak unto Esau thy brother, saying, bring me venison, and make me savoury meat, that I may eat, and bless thee before the LORD before my death.
Now therefore, my son, obey my voice according to that which I command thee. Go now to the flock, and fetch me from thence two good kids of the goats; and I will make them savoury meat for thy father, such as he loveth: And thou shalt bring it to thy father, that he may eat, and that he may bless thee before his death."
Jacob is uncomfortable with this instruction, fearing his father's reaction, and is reassured by his mother that
"Upon me be thy curse, my son: only obey my voice, and go fetch me them"
Rav Mordechai Breur (z"tl) in his Pirkei Bereshit (Chapters of Genesis) points out Jacob's deception of his father was not an independent action, but rather was an one born of obediance to his mother's command. It is not Jacob who creates the plan, but rather his mother, who sees that Isaac is about to give his materialistic and non-spiritual son his final blessing, which in her opinion will be a mistake.
Seen in this light, Jacob's actions do not seem morally reprehensible at all. Whilst a child does not have the right to steal from a sibling or to deceive a parent, a mother does have the right to influence the family's decision making process. Rebaka sees that Isaac is about to make a mistake and takes action.
But why deception? Could Rebaka not have approached Isaac and argued her case? Rav Breur (z"tl) suggests that in the societal conditions within which our text is set, a woman did not have the ability to openly contradict her husband. Thus Rebeka, with the added pressure of Esau returning soon, decides that Jacob must deceive his father.
Rav Breur (zt'l) points out another case in Genesis where a woman is forced to take deceptive action. In Parshat Vayeshev (chapter 38), we find another story of a woman's deception:
"And Judah took a wife for Er his firstborn, whose name was Tamar. And Er, Judah's firstborn, was wicked in the sight of the LORD; and the LORD slew him. And Judah said unto Onan, Go in unto thy brother's wife, and marry her, and raise up seed to thy brother. And Onan knew that the seed should not be his; and it came to pass, when he went in unto his brother's wife, that he spilled it on the ground, lest that he should give seed to his brother. And the thing which he did displeased the LORD: wherefore he slew him also. Then said Judah to Tamar his daughter in law, Remain a widow at thy father's house, till Shelah my son be grown: for he said, Lest peradventure he die also, as his brethren did. And Tamar went and dwelt in her father's house."
Tamar, who has been widowed and does not have children, is promised by her father in law Judah his third son to have a child with, but the text tells us that Judah does not intend to give his third son to her.
Tamar takes action into her own hands:
"And it was told Tamar, saying, Behold thy father in law goeth up to Timnath to shear his sheep. And she put her widow's garments off from her, and covered her with a vail, and wrapped herself, and sat in an open place, which is by the way to Timnath; for she saw that Shelah was grown, and she was not given unto him to wife. When Judah saw her, he thought her to be an harlot; because she had covered her face. And he turned unto her by the way, and said, Go to, I pray thee, let me come in unto thee; (for he knew not that she was his daughter in law.) .... and she conceived by him."
Thus Tamar must deceive her father in law Judah in order to obtain what is rightly hers.
We can also see that in both stories, the deception is temporary. Isaac and Judah both find out about the deception, Isaac "was seized by a very violent trembling" and Judah initially decides that Tamar should be brought forth, "...and let her be burnt". But their initial reactions do not last. Isaac and Jacob are reconciled in Chapter 28, when Isaac sees the wives Esau has taken, and understands Rebeka's action, finally blessing Jacob. Judah too, when confronted with evidence that it is he who Tamar has conceived from, immediately says "She hath been more righteous than I; because that I gave her not to Shelah my son".