Unbreakable Vows in Harry Potter and in Judaism (Matot)

In Harry Potter and the Half Blood Price (the sixth book) we learn about unbreakable vows. In chapter 2 we see how Professor Snape takes an Unbreakable Vow: (some details skipped so as not to spoil it for those who haven't read it)

"Certainly, ... I shall make the Unbreakable Vow," he said quietly. "Perhaps your sister will consent to be our bonder... You will need your wand."
...
"Will you, Severus, watch over .... ?"
"I will," said Snape.

A thin tongue of brilliant flame issues from the wand and wrapped around their hands like a red-hot wire.

"And will you, to the best of your ability, protect... ?"
"I will," said Snape.

A second tongue of flame shot from the wand and interlinked with the first, making a fine, flowing chain.

"And, if it should prove necessary ... will you... ?"
"I will," said Snape.

A third tongue of flame shot from the wand, twisted with the others, and bound itself thickly around their clasped hands, like a rope, like a fiery snake.

And later we read Ron's simple explanation to Harry of what Unbreakable Vows
are:

"An Unbreakable Vow?" said Ron, looking stunned... "Are you
sure?"

"Yes, I'm sure," said Harry. "Why, what does it mean?"

"Well, you can't break an Unbreakable Vow...."

"I'd worked that much out for myself, funnily enough. What happens if you break it, then?"

"You die."

The idea of vows that magically bind a person's soul is found explicitly in the Torah, in the Torah portion of Matot (Matos). As the Torah tells us (Num 30:3):

"If a man makes a vow to G-d, or makes an oath to prohibited something to his soul, he must not break his word, whatever he says must be done."

Commentaries elaborate that vows and oaths include commitments to do certain things and commitments not to do certain things. If someone makes a vow or oath not to eat a certain food, for example, that food becomes as prohibited as pork. If someone makes a vow or oath to go to a certain place at a certain time, going to that place at that time becomes as required as any other commandment.

Oaths and vows are so important in the Torah that Jews have adopted the practice of never making them, even for things that they intend to carry out, because of not wanting to take any risk of breaking an oath or vow. As an example, on the back cover of Harry Potter and Torah I pledge to give a tenth of my profits from book sales to schools that educate English-speaking children living in Israel, but I specified that this pledge was not a Torah oath, just a pledge.

This is also the source of one of the most famous and well-attended prayer services of the Jewish year, Kol Nidrei, on Yom Kippur eve. Said right before the onset of the Yom Kippur holiday, the prayer specifies that we want to release ourselves from any vows or oaths that we've made that we didn't mean to make, and that we enter the new year with the desire not to commit ourselves to any vows or oaths that we may make mistakenly. Many of the things that people want atonement for on Yom Kippur relate to rash decisions, sometimes oaths or vows, that are made in the heat of the moment and which we later see to be mistakes. In Kol Nidrei we start the day of atonement with a request that G-d release us from all of these vows or oaths that we should not make.

Of course, for vows and oaths, and for all Torah laws, the Jewish perspective on reward and punishment is more complicated than Unbreakable Vows in the Harry Potter world, for which someone simply dies when violating. The Torah views the world as more complicated than simply "do this, you die." But like in Harry Potter's world, the Torah sees vows and oaths as very important, binding the person's soul to the promise made.

I'm not going to speculate how Snape's Unbreakable Vow will resurface in the final book, Harry Potter and the Deathly Hallows. Would Snape have killed Dumbeldore if he had had the option of attending a Kol Nidrei prayer service? We may never know.

But Jews don't need magical spells to commit to things, as the Torah says, whatever we say should be done. By taking our commitments seriously, our words take on a magical force of their own.