Why Red Blood Comes From White Bones: A Spiritual and Biological Insight into the Human Body

The human body is essentially composed of a framework of white bones, covered by red flesh.

Thus, a person is formed of an inner kindness (chesed) and an outer “strength” or restraint (gevurah). It is wondrous that the red blood is produced specifically within the white bones. From a spiritual perspective, this teaches that gevurah itself emerges from chesed.

The attribute of gevurah, which manifests as judgment and sometimes suffering in the world, ultimately stems from benevolence, just as the attribute of kindness does. Through judgment and hardship, a person is cleansed of the stains of sin and elevated toward a clearer understanding of the purpose of life. This reflects the verse: “Hashem (the Name of mercy) is God (the Name of judgment)”—meaning that judgment itself is, at its core, an expression of mercy. (Kings I 18:39)

On the other hand, red blood contains white blood cells, whose role is to defend the body against harmful bacteria. The red blood cells supply oxygen and nourishment to all the cells of the body, sustaining and enlivening them. This corresponds to the attribute of gevurah, the measure of judgment.

For the Creator, who brought all beings into existence, is obligated, as it were, to sustain them, this sustenance corresponds to the aspect of judgment. Yet the white blood cells, which destroy invading bacteria, represent chesed: not only does the Creator provide for His creations, but He also protects them, eliminating external enemies that arise as a consequence of human actions. (Shaarei Teshuvah by Rabbeinu Yonah of Gerona.)