There are multiple biblical obligations to actively save the life of another and not stand by your brother’s blood (Vayikra 19:16).
The Talmud in tractate Sanhedrin (73,a) teaches that one is obligated to be willing to endanger himself to some extent in order to save another’s life, by doing such acts as jumping into a river to save someone who is drowning, or warding off wild predators or bandits, even though all of these acts involve some level of danger. A person is not obligated, however, to save his fellow if it puts him in great danger. The exact parameters of a great danger are discussed in Jewish Law but they are clearly greater than fighting off bandits or a wild animal. We would not want another to be overly cautious when considering whether or not to save our life and we must be willing to do the same for another, as long as the danger is not considered a great danger.
To give a meal to a starving person is an obligation. To give a lobe of one’s liver is permissible but not required due to the risk involved. How about a pint of blood if that person needs your pint of blood to live? What about a kidney? What about bone marrow?
G-d gave you the incredible opportunity to give another a second chance at life by giving your bone marrow. (The extraction of bone marrow carries almost no risk to you. You only give a few percentages of your body’s bone marrow and it regenerates quickly). Bone marrow is the soft, spongy material found inside bones. Bone marrow contains stem cells that give rise to white blood cells (to fight infections), red blood cells (for oxygenation) and platelets (to prevent hemorrhaging). The chief function of bone marrow is to produce blood cells. The other chief function of bone marrow is to give you the chance to give LIFE to another!
What an opportunity and mitzvah to give another the gift of life!
Menachem Mendel Bluming