ויקרא פרק יט, טז לֹא תַעֲמֹד עַל-דַם רֵּע ךָ
The Gemara (Sanhedrin 73a) references this verse to the case when one sees a person drowning in the river or a wild animal is dragging a person, or robbers have come upon a person, one must take steps to save the person in mortal danger. The verse means that if one sees someone in danger, then one should take actions to save that person and not see their blood spilt.
It is obvious that the above case involved a person drowning in a river against his will. However, is one obligated to save a person that is drowning by their own hand (i.e. suicide), for example, due to the heavy burdens of life, or sickness, etc?
Perhaps one could derive an answer from the Gemara (Kesuvos 67b) when a person who has money but refuses to spend the money, we are not obligated to support that person from communal charity funds, even though that person might die of starvation.
However, the Sefer B’samim Rosh (attributed to the Rosh) says that a person who declared before two others that he lacks food and drink and that his life is not worth living and then goes and kills themselves, such a person is not called a willful suicide.
An opinion exists that in the case involving a person attempting to end their life due to a very serious sickness without hope of recovery and is suffering great pain, another is not obligated to prevent their death. And for this opinion there is support from the statement of the Ran (Nedarim 40a) that there are times that it is necessary to daven/pray for a sick person that they should die, for example, a sick person without hope of recovery who is suffering much pain.
Therefore, if it permitted to pray for a person that they should die, then, certainly one does not have to save a person that is drowning oneself in the river due to great pains for a life-ending sickness.
It should also be known what the Radbaz wrote in a teshuvah (brought in C.M. 425) in the matter of “not standing idle by the blood of another” that this also obligates one to save the property (money) of others that one sees is being lost or destroyed. This is implied from the word דמים which contains two definitions: physical blood, and to property (money).
