The Torah obligates us to do everything possible to save lives, including incurring financial loss (in fact, according to the Chafetz Chaim, a person is obligated to spend all of his money to fulfill this mitzvah). He may not spare any effort in doing so. The source of this obligation is the Pasuk, “Lo Sa’amod Al Dam Rei’echa – Do not stand idly by the blood of your fellow”.
For those who are not medical professionals, the practical obligation of “Lo Sa’amod Ad Dam Rei’echa” usually expresses itself in the form of a duty to contribute financially to those whose lives are threatened, or to exert themselves on their behalf. In the case of security guards or emergency responders, there is sometimes a need to risk their lives to save others. In fact, a layperson can sometimes encounter a situation when he would need to risk his own life to save others, such as if a person is drowning. In all of these cases, it is important to know the extent of one’s obligation.
The Poskim discuss this topic in great detail. We have discussed it in several previous essays; we will not elaborate on it again here. As a general rule, if the lifesaving attempt would involve minimal risk to the rescuer and is likely to be successful, it is proper to attempt it.
A related question is whether there is an obligation to donate an organ to save another person’s life (if the process will not endanger the donor). We have previously discussed that although the danger to the donor is minimal, and it is highly encouraged by Rabbanim and physicians alike, there is no obligation to donate a kidney to another. We cited the Radvaz (Shu”t, 3:627) who discusses the extraordinary case of a man who was told by a violent aggressor to give up one of his limbs (in a way that would not endanger his life) or else his friend would be executed. After noting that cutting off a limb should in fact constitute [at least a Chashash] Sakana, the Radvaz adds another important principle:
Furthermore, it says in the Pasuk (describing the Torah) ‘Deracheha Darchei Noam – its ways are pleasant’. This means that the laws of the Torah must be consistent with basic logic and reason. How then could it occur to us to say that a person should allow his eye to be blinded or his arm or leg to be amputated in order that somebody not kill his friend?
Therefore, I do not see a reason to rule [that he must lose a limb in order to save his friend]. To do so would be an act of extreme piety. Fortunate is the lot of the person who would stand up to such [a challenge].
Moreover, if there is any possibility of danger to himself [due to the amputation], to acquiesce would be the act of a ‘Chasid Shoteh’ (pious fool).
In that essay we attempted to explain the “basic logic and reason” that the Radvaz invokes to exempt a person from cutting of a limb to save his fellow Jew, despite the fact that the Torah does obligate a person to incur expenses to save lives, and his life would not be at [significant] risk if he would do so. We suggested that the Radvaz means to establish an important principle, namely, that unlike financial outlay or effort, a person’s body is not a “resource” to be used for saving lives. It has a purpose and mission – life itself.
However, while this suffices to exempt a person from sacrificing a limb to save somebody else’s life, it does not explain why he would not be obligated to donate a “renewable” part of his body, such as blood or bone marrow. This question is the subject of a wide-ranging Machlokes haPoskim. We will present several views below.
There is a comprehensive and fascinating Teshuva from Rav Shmuel Wosner zt”l (Shevet haLevi 5:219):
It is common to have a patient whose life is in danger and who needs a blood transfusion. In particular, if the patient has an unusual blood type which is not commonly found in blood banks, and can only be procured from select individuals and sometimes from far away; and there are cases where, due to Sakana, [a patient] needs erythrocytes (red blood cells). This is obtained by taking blood from a healthy person with a special machine for several hours, then returning the blood to him. They remove the erythrocytes and give them to the sick patient. You are questioning whether a person refrains from this (donating [whole] blood or erythrocytes) due to weakness, or bother, or fear, has transgressed “Lo Sa’amod Al Dam Rei’echa”.
After elaborating on the question of potential self-endangerment to save lives, Rav Wosner asserts that donating blood is not even a “Safek Sakana”. In fact, the Gemara relates that bloodletting was a common practice even among healthy people (Shabbos 129). If it was dangerous, it is unlikely that it would have been a common practice. Moreover, it is clearly evident that donating blood does not pose any risk to a person’s life (though the specific donation that Rav Wosner discussed might theoretically have some sort of Sakana).
Rav Wosner then begins a fascinating discussion as to whether a person is obligated to become sick (though not dangerously) in order to perform Mitzvos. His conclusion is that one is indeed obligated. (We have discussed this question at length elsewhere.) In particular, with regard to saving lives he rules that one is absolutely obligated to tolerate sickness in order to fulfill the Mitzva:
Ultimately, with regard to the precept of “Lo Sa’amod Al Dam Rei’echa”… it is obvious [that one is obligated]. For it is only with regard to a situation of Sakana or even Safek Sakana that a person should not endanger himself for the sake of saving his fellow. But [if he will only become] a Choleh sheEin Bo Sakana, he is certainly obligated (even if we do not say this with regard to other Mitzvos). Regarding your main question concerning a standard blood donation – it is certainly a Mitzva…
With regard to bone marrow donation, Rav Shlomo Zalman Auerbach zt”l advised that one explain to a potential donor that it is a great Mitzva to donate. If the chances that the bone marrow will help save a life are greater than 50%, one should implore him to overcome his fears and fulfill the great Mitzva of Pikuach Nefesh. However, one must not coerce the potential donor or put him under duress at all, including psychological or social pressure, given his fear of the very slight risk to his life from the necessary general anesthesia. However, if his only concern is suffering or even the pain, it may be permissible to obligate him to donate if there is nobody else who can do so.
In “Asya” 53-54 (Elul 5754) Rav Avigdor Nebenzhal Shlit”a relates:
In my youth I was sent to the Brisker Rav zt”l by my mother to ask him if one may try to influence somebody to donate blood. His response was that one may say to somebody, “So-and-so needs blood.” However, one should not pressure him to donate blood, even [just] with words.
However, Rav Avraham Goldmintz contends (in his Sefer, “b’Damayich Chayi, p27, footnote 35) that in the days of the Brisker Rav they considered it dangerous to donate blood. Today this is clearly not the case, thus one cannot draw any conclusions from the Brisker Rav’s ruling.
By contrast, the Teshuva of the Tzitz Eliezer (16:23) who also addressed this question, is still relevant today. He maintains that one cannot obligate a person to donate more than a Revi’is of blood because that volume is considered the “Nefesh”. Asking him to donate this amount of blood for the sake of a Mitzva is like asking him to give a Shiur of his very life away!
Then he adds: “Truthfully, we do not find anywhere that a person has an obligation to donate his blood for the sake of fulfilling a Mitzva.” He does not indicate whether this reasoning augments his first argument or whether it stands alone. In other words, is there a principle that one is not obligated to donate a part of his body for the sake of a Mitzva or does this only apply to blood which constitutes the “Nefesh”?
In truth, the argument that since the blood constitutes the “Nefesh” a person is not obligated to give it away, needs further scrutiny. Since donating a Revi’is of blood does not present any kind of Sakana, why should the fact that it is considered the “Nefesh” make any difference?
Either way, a closer examination of the Teshuva reveals that the Tzitz Eliezer’s main concern was that he considered donating blood to be something of a Sakana. He disagrees with Rav Wosner’s contention that the fact that the Gemara records bloodletting as a standard procedure and the fact that it does not present any Sakana today, indicates that there is no Sakana:
In light of all that has been said, it appears to me that [the response to] the question you asked is: A person who has a weaker constitution has no obligation to donate blood for a dangerously ill patient who needs a rare blood type which cannot be obtained elsewhere. In fact, it may even be forbidden for him to do so since it is probable that he will be harmed by it and will [become sick and] be confined to his bed. This [procedure] may lead to a “shock to his entire organism” and it is likely that Sakana will soon follow (perhaps even after several years) – it will not be known that this occurred because of taking this blood from his body.
The Tzitz Eliezer also disputes Rav Wosner’s contention that “[If a person will only become] a Choleh sheEin Bo Sakana [by donating blood], he is certainly obligated, even if we do not say this with regard to other Mitzvos.” He argues that is logical to assume that one would not be obligated to make oneself unwell to avoid passively violating a regular Mitzvas Asei or Lo Sa’asei. In other words, there is no reason to distinguish between the Mitzva of “Lo Sa’amod Al Dam Rei’echa” and other Mitzvos in this regard.
He also cites the Ya’avetz (Migdal Oz 3, Even Bochen 1:83) who rules that a person is not even obligated to endure humiliation in order to save somebody’s life, though it is a Mitzva. This appears to support the Tzitz Eliezer’s contention that there is no difference between the Mitzva of “Lo Sa’amod” and other Mitzvos in this regard. If a person is not obligated to endure humiliation to save a life, he is certainly not obligated to become ill in order to do so.
In conclusion, we have presented various opinions on this matter and it is difficult to decide between them. We must point out that not every situation is the same. In some cases, there is still a reserve supply of blood or bone marrow, thus there would be no reason to say that another person must donate. In other cases, the potential donor has a very rare blood type, and in that case it may be possible to coerce him to donate if it will not harm his health to do so.
 In his Sefer Ahavas Chesed
 See Bo 5779, Tazria 5780, Sukkos 5781, and Tazria-Metzora 5781
 Mishlei 3:17
 [Editor’s note: It is unclear what exactly Rav Wosner zt”l is referring to, as modern blood donation of concentrated red cells using an automated process that separates the erythrocytes from the plasma and platelets and returns those other components to the donor generally takes under an hour and presents little risk to the donor due to screening and eligibility requirements. It is worth noting that although this Teshuva is undated, this volume of the Shu”t was published in 1983, and technology has advanced significantly in the intervening four decades.]
 Nishmas Avraham 4, E.H. 80.