The Gemara in several places justifies a Halacha with the phrase lo nitnah Torah lemalachei hasharet – the Torah was not given to the ministering angels. I explored the parameters of this principle in a shiur available: here. (For those who followed this year, this is related to last year’s series on Psak – this year’s series with begin after chagim.) Christine Hayes discusses this topic (here), and I mention several points from that presentation.
Before we get to the actual legal application of this principle, it is important to note that Chazal have a backstory to this. The famous Midrash (found in many places in Chazal in different forms, I focused on the one in Shabbat 88b-89a) tells about the argument between God and the angels when God decided to give the Torah to man. They claimed that man did not deserve this jewel that had remained in heaven for so long. God commands Moshe to respond to them. He shows them the Torah is made for human beings – people with desires that need to be controlled, parents that must be honored, with a history that must be remembered (Miztrayim), and so on. The angels give in and shower Moshe with gifts. Hayes notes that this notion – that human beings were an ideal of sort, that they had advantages over angels, but uniquely rabbinic. The sectarians, or for that matter the Greeks, thought that humans should strive to be angels. Chazal celebrated that the Torah was given to humans, limitations and all.
The Gemara uses this phrase in four contexts, three of which are related. Two relate to saying shema. One allows someone to say shema even if his “foot sees his erva” – though here this conclusion is subject to a dispute. In the second, the Gemara allows someone to say shema if there is feces on this inside of the body that only protrudes if he sits. The third leads the Gemara to conclude that Kohanim must be allowed to benefit from the begadim, the garments they wear during avodah, because otherwise they would have to strip the second they finished any activity in the mikdash. In all these cases, the Gemara argues that something must be permitted because of lo nitnah.
Rav Asher Weiss notes correctly that in none of these cases is it impossible to be “angelic” – it is just difficult. The clearest example is the first case, where there is actually a dispute about whether it is permitted – meaning it must be possible. However, as Rav Mosheh Lichtenstein noted, this only makes it more important to figure out the parameters of this principle – it can’t be (and in fact is not) true that the Torah never expects us to do something difficult!
Rav Mosheh suggested that these cases are unique as they relate to avodah or tefillah – in both cases you might have expected God wanted us to be angelic – but in the end, God wants humans and thus recognizes the limitations of the human body and accommodates it. (I think this was what he said – but he did not remember his formulation either, so I reconstructed it as best I could.) This emerges clearly from Tosafot and the Rambam who both think that while one does not have to rip off the regular bigdei kehunah, one does have to quickly take off the avnet which has shaatnez. In other words, it is something about avodah/meilah that has a built in limitation. Hayes comes at it from another angle – in these cases, if there was no dispensation, one would not daven or serve. The principle comes to remove an excuse not to serve – not to allow the perfect to become the enemy of the good. A third point to note is that all these things stress the natural limits of the human body, which works with what we said above.
[The fourth case in the Gemara explains that we don’t sanctify things made for the mikdash until after they are built, as it is difficult to properly treat holy things. Here there is not issur involved, but the pragmatic advice does work in the same direction – recognizing the limitations of normal people.]
Taken together, I think this principle is not always predictive (and if you listen to the shiur, you will see how some of the cases in psak are hard to pin down), but it does provide a general direction. The Torah is given to human beings and there are natural limitations to our bodies and routines. Poskim use this phrase when they are convinced that a certain rule cannot mean something which is so beyond the realm of what people can do or can be expected to do. Sometimes the actual mechanism they are using is bittul, sometimes it is ones, but at some level these are related.
I then brought a teshuvah by Rav Asher Weiss where he presents a general thesis that the Torah expects things to be gauged by average people with normal lives and normal abilities. He provides many sources in kashrut, niddah, and elsewhere where we allow people rely on their normal faculties. Thus, people with average sight can rely on their own senses to see whether there are bugs in vegetables (he argues here on the claim that while the Torah was not given to angels, it was given to the most super human humans). By Niddah, we allow normal poskim to look and see if they think something is red. Women are also not expected to do bedikot in impossible ways. Moving to the recognition of human routine, he notes that Rashi explains the reason people who wear tefillin all day (the original obligation) can simply put their tefillin on the side if they need to nap is because it is normal to nap, thus there must be a natural way to store tefillin while doing it.
I will not go through all the examples, though the teshuvah is provided in the sources.
He does note that there are some cases where it must be that we do not employ this principle. For example, when determining death, we use the best tools available, and do not simply take our best guess using the naked eye. Presumably this is related both to the severity of human life and the fact that the Gemara’s suggestions as to how we test death were probably just that – tests. If we have better ones, we use them. Many students pointed out that the former factor must be more important, because in the bug case, we are also asking about what tests qualify to determine what is bug free. Again, I think the best I can do to explain the differences is to admit that this principle is not predictive but points in a direction. Poskim will use their own intuition to explain what things are human and what are superhuman (and when we can be expected to be superhuman). There are many mechanisms that legally generate conclusions that accord with this principle and each must be understood and applied with care. The result, however, is a system that embraces that Torah was ideally given to those flawed human beings who need it and with it can become great.