Sávuot / smirát hánefes

For your own sake, therefore, be most careful—since you saw no shape when יהוה spoke to you at Horeb out of the fire—

The Sages taught: There was a related incident, involving a particular pious man who was praying while traveling along his path when an officer [hegmon] came and greeted him. The pious man did not pause from his prayer and did not respond with a greeting. The officer waited for him until he finished his prayer.After he finished his prayer, the officer said to him: You good for nothing. You endangered yourself; I could have killed you.
Isn’t it written in your Torah: “Take utmost care and guard yourself diligently” (Deuteronomy 4:9)?
And it is also written: “Take therefore good heed unto yourselves” (Deuteronomy 4:15)? Why did you ignore the danger to your life?
When I greeted you, why did you not respond with a greeting?Were I to sever your head with a sword, who would hold me accountable for your spilled blood?

But take utmost care and watch yourselves scrupulously, so that you do not forget the things that you saw with your own eyes and so that they do not fade from your mind as long as you live. And make them known to your children and to your children’s children:

Rabbi Dostai ben Rabbi Yannai said in the name of Rabbi Meir: whoever forgets one word of his study, scripture accounts it to him as if he were mortally guilty, as it is said, “But take utmost care and watch yourselves scrupulously, so that you do not forget the things that you saw with your own eyes” (Deuteronomy 4:9). One could [have inferred that this is the case] even when his study proved [too] hard for him, therefore scripture says, “that they do not fade from your mind as long as you live” (ibid.). Thus, he is not mortally guilty unless he deliberately removes them from his heart.

Our Sages forbade many matters because they involve a threat to life. Whenever a person transgresses these guidelines, saying: "I will risk my life, what does this matter to others," or "I am not careful about these things," he should be punished by stripes for rebelliousness.

§ The Gemara discusses whether it is permitted to injure oneself. And is a person not permitted to injure himself? But isn’t it taught in a baraita: One might have thought that if one takes an oath to do evil to himself and did not do evil he will be exempt from bringing an offering for having transgressed this oath. Therefore, the verse states: “Or if anyone swear clearly with his lips to do evil or to do good” (Leviticus 5:4), which teaches that just as taking an oath to do good for which one is liable is referring to an optional activity, as opposed to taking an oath to perform a mitzva, so too, taking an oath to do evil is referring to an optional activity, as opposed to taking an oath to transgress. I can therefore include within the category of one who is liable if he transgressed his oath the person who takes an oath to do evil to himself and did not do evil. It is clear from this baraita that doing evil to oneself is permitted.

It is a positive commandment to make a fence on one's roof as it says "and you shall make a fence for your roof". This applies if it is a dwelling place, but a storage house or a cattle house and the like do not require one.

The Gemara presents the first incident: Rabbi Zakkai was once asked by his disciples: In the merit of which virtue were you blessed with longevity? He said to them: In all my days, I never urinated within four cubits of a place that had been used for prayer. Nor did I ever call my fellow by a nickname. And I never neglected the mitzva of sanctifying the day of Shabbat over wine. I was meticulous about this mitzva to the extent that I had an elderly mother, and once, when I did not have wine, she sold the kerchief that was on her head, and from the proceeds she brought me wine upon which to do the mitzva of sanctifying the day.