The firstborn has an inviolable right to his share of his father’s inheritance. The Torah is teaching us that rivalries or animosities do not determine the laws of inheritance. There is a clearly defined halachah that the firstborn receive a double portion of his father’s inheritance. The fact that his father harbors a hatred for his mother does not give him license to deprive his firstborn son of his rightful share. In forbidding the father to give over a firstborn’s rights, the Torah uses a puzzling term. It says, lo yuchal, “He is unable to do so.” Why is the word “unable” used, as opposed to another term that simply says he cannot do so.
Horav Eliyahu Meir Bloch, z.l., explains this concept with an analogy: If someone tells a man who is standing on top of a roof high above the ground to jump off, he will not simply reply by saying, “I do not want to jump”; he will, rather, say “I am unable to.” He is so certain of his impending death if he jumps, that the knowledge alone serves as a powerful restraint. He is unable to jump, because he clearly sees the consequence of that jump. The same concept applies to mitzvos and aveiros, sins. One who views an idea as an absolute fact cannot begin to fathom it in another perspective. Thus, if we view mitzvah fulfillment as a fact, then we are unable to consider transgressing it. One who sins does not view the Torah’s commandments as fact. Hence, those who have rewritten the Torah to suit their needs did so after first conjuring up a convenient philosophy that the Torah is not immutable, that it is not from G-d, that it is not an absolute.
The Torah teaches us that our attitude towards sin must be such that we are unable to transgress the commandments. We see the reality of sin; we are acutely aware of the consequences. This knowledge should serve as a powerful restraint.