When God created the universe, the life it contained was not equally instructed. The amphibians and birds were told:
וַיְבָרֶךְ אֹתָם אֱלֹהִים, לֵאמֹר: פְּרוּ וּרְבוּ, וּמִלְאוּ אֶת-הַמַּיִם בַּיַּמִּים, וְהָעוֹף, יִרֶב בָּאָרֶץ – God blessed them saying, “Be fruitful and multiply; fill the waters of the seas, and multiply the land”. (1:22)
In contrast, mankind was told:
וַיְבָרֶךְ אֹתָם, אֱלֹהִים, וַיֹּאמֶר לָהֶם אֱלֹהִים פְּרוּ וּרְבוּ וּמִלְאוּ אֶת-הָאָרֶץ, וְכִבְשֻׁהָ – God blessed them; and God said to them to be fruitful and multiply; fill the land and conquer it… (1:28)
The Netziv points out that while both are blessed to be populous, man had a personal instruction – וַיֹּאמֶר לָהֶם – it was said to them directly, and not just about them.
Rav Hirsch notes that nature serves God by its intrinsic existence. It cannot be otherwise because there is no deviation in how it relates to God. Mankind however, is spoken to, and must choose to listen. Free will is the צלם אלוקים that distinguishes humanity from other creatures. Allowing instinct and nature to run wild is to surrender to the animal within; the charge is to subjugate it and listen to God’s instruction.
The Netziv explains that the animal instinct within us must be channeled a particular way, as evidenced by the origin of humanity:
וַיִּיצֶר יְהוָה אֱלֹהִים אֶת-הָאָדָם, עָפָר מִן-הָאֲדָמָה, וַיִּפַּח בְּאַפָּיו, נִשְׁמַת חַיִּים; וַיְהִי הָאָדָם, לְנֶפֶשׁ חַיָּה – God formed man from the dust of the earth, and breathed into him a living soul, and the man became alive (2:7)
Animals are simply called נֶפֶשׁ חַיָּה – they are living things. But mankind is made of more – a balance of mundane matter, pumped with soul. It is with this equilibrium that man becomes truly alive. The word חַיָּה means alive, but it also means happy. The happiness is found in the balance. This is the choice on offer – וַיֹּאמֶר לָהֶם.
This is reflected in their respective developments too; a newborn calf can stand not long after birth, and while it will get bigger, it is born as it will always be; whereas humans are born helpless, defenceless, and pretty useless for a relatively large part of their lives. Clearly, mankind are intended for greater aspirations than cattle.
The Torah is intended as instructions on how to live. The Gemara teaches that וָחַי בָּהֶם – in most circumstances it is better to violate the Torah and live than die for its sake, with the exception of three cardinal sins: idolatry, murder, and consummating forbidden relationships. Bizarrely then, the location of the principle וָחַי בָּהֶם is exactly where it doesn’t apply, in the opening portion of forbidden relationships:
כְּמַעֲשֵׂה אֶרֶץ-מִצְרַיִם אֲשֶׁר יְשַׁבְתֶּם-בָּהּ, לֹא תַעֲשׂוּ; וּכְמַעֲשֵׂה אֶרֶץ-כְּנַעַן אֲשֶׁר אֲנִי מֵבִיא אֶתְכֶם שָׁמָּה, לֹא תַעֲשׂוּ, וּבְחֻקֹּתֵיהֶם, לֹא תֵלֵכוּ. אֶת-מִשְׁפָּטַי תַּעֲשׂוּ וְאֶת-חֻקֹּתַי תִּשְׁמְרוּ, לָלֶכֶת בָּהֶם: אֲנִי, יְהוָה אֱלֹהֵיכֶם. וּשְׁמַרְתֶּם אֶת-חֻקֹּתַי וְאֶת-מִשְׁפָּטַי, אֲשֶׁר יַעֲשֶׂה אֹתָם הָאָדָם וָחַי בָּהֶם אֲנִי, יְהוָה – As Egypt did when you lived among them; do not do. And as Canaan do, when I bring you there, do not do; do not follow their ordinances. It is My law that you should do, and My ordinance that you should observe, and follow its ways; I am The Lord. Guard My law and ordinance, that you will do them, and live by them; I am The Lord. (18:3-5)
Literally anywhere else in the entire Torah would be appropriate to teach וָחַי בָּהֶם. Why does it appear here with respect to the section of forbidden relationships?
Arguably, it makes the most sense to include it by its exception – it serves to prove the rule itself. God grants life – but life isn’t everything. What matters is the way the life is lived. The three exceptions contradict the essence of life.
The section וָחַי בָּהֶם is said of is not entirely limited forbidden relationships. Apart from incest, the end of the laws address homosexuality, bestiality, and sacrificing children to Molech, a form of idol worship.
They are not an acceptable way of life. All are squandering and snuffing out potential life for transient and questionable gain. Perhaps it could be said that the man has embezzled a part of himself as well – that is not the person God intended to create. וַיֹּאמֶר לָהֶם – there was meant to be a balance of the mundane dust of physicality married to the spiritual soul, and that couldn’t be further from these. They are the ultimate obfuscations and literal perversions; funnelled into narcissism and self pleasure. What sort of human being puts a child, his own flesh and blood, into a fire, for some sort of spiritual elevation?
וָחַי בָּהֶם is placed on these to indicate the requirement of a direction in life. Life does not trump everything. Because there is another exception to וָחַי בָּהֶם too – during Shmad, a time of persecution and genocide. Rather than violate even the smallest and most insignificant law, a Jew should sacrifice their existence. Because life has to be worth something.
And if you don’t stand for something, you’ll fall for anything.