This is a complex and intricate discussion. 

The field of medical ethics has determined that the foremost principle is do no harm. Kidney donation is a medical procedure that provides no benefit to the donor. Not only is there no benefit to the donor, but there is injury – albeit small – involved in the process itself, since we are dealing with anesthetics and an invasive procedure with the risk for infection, as well as long-term damage from the very fact that the person will be left with one kidney. It is possible that this kidney will not be able to last him his entire life, and he may find himself in need of a transplant. If this indeed was the only factor – there would be grounds to prohibit encouraging kidney donation altogether, and by logic the donation itself.

However, this viewpoint is incredibly narrow, for alongside medical ethics we have a biblical mitzvah that also functions as an ethical principle, “do not stand idly by your friend’s blood”. This mitzvah obligates man to take a certain degree of risks in order to save his friend: “and from where [do we know that] if one sees someone drowning in a river or robbers or a wild beast confronting them, you are obligated to save them? The verse teaches ‘do not stand idly by your friend’s blood’” (Sifra Kedoshim). Throughout history many responsa have been written regarding the level of risk that a person must assume in order to save their friend. The basis of the discussion is determined to be bringing oneself to the level of potentially life-risking act in order to prevent my friend’s definite life-risking act. The accepted opinion of the poskim (the most famous responsum is that of the Radbaz, 3:627) is that there is no absolute obligation to perform this, and it is even antithetical to the verse “[The Torah’s] ways are ways of pleasantness, and all its paths are peace”, however this is “a pious level and bountiful is the portion of one who can fulfill this”. Yet, the Radbaz walks back his statement “and if there is a risk to life it is a pious fool who [believes] that a risk to them is worth the definite [danger] of their friend”. 

This response means that practically one must consider in each event the level of distress and risk the person is confronted with opposite the required level of risk in order to save them. When dealing with great risk by the life-saver – it would be proper not to put oneself at risk. Yet, if the risk is low – this is a pious matter to perform. As stated, many of these issues have been discussed in the past, and even within the Radbaz himself the matter is not well-defined, however it seems that a significant majority of poskim agree with this principle. Due to the fact that kidney donation comes with little risk – the majority of poskim have determined it to be permissible, and therefore the accepted position is that one is not obligated in donating a kidney, yet one who abstains does not violate the negative commandment, “do not stand idly by your friend’s blood”. 

Does this position open the discussion of encouraging kidney donation? It seems that due to the fact that we are dealing with a just and proper pious matter – this is permitted and encouraged. However, one must be careful, as reinforcement may cause people to try and donate a kidney even if their personal risk is much greater, or if they feel pressured and do not actually want this. This is part of the prohibition “before a blind man do not place a stumbling block” where one of the examples brought in the Midrash Halacha is “if they are asking for advice from you, do not provide inappropriate advice to him”. Therefore, the reinforcement must be generalized and focus on the greatness of one who donates a kidney. However, providing direct encouragement is forbidden.

For additional reading:

• Position Paper: Organ Donation
• “I Am with Him in Suffering”: The Accompaniment of the Sick According to Jewish Sources
• Organ Donation: Nobility that Trumps the Pain