Is the "nadhrah" (radiance/beauty) in the Hadith: "May Allah make radiant/beautiful a person who hears my words, comprehends them, and then conveys them as he heard them" a physical beauty, a spiritual glow of the face, or does it encompass both?

The Prophet, peace and blessings be upon him, specifically invoked a prayer for radiance for those blessed with knowledge and understanding of the Prophetic Sunnah (definition), due to the high status and position they hold in this world, and the blessings they will receive in the Hereafter. Radiance encompasses both outward and inward beauty. It is the joy and comeliness that graces the face as a result of faith, and the inner delight, joy, and pleasure of the heart, and its enjoyment of it. Thus, bliss and a good heart manifest as radiance in the face.