Saint Onophrius (1642) by Jusepe de Ribera - Public Domain Catholic Painting

Ribera painted many half-length images of saints for Catholic patrons, most likely for private worship. Here he rendered the hermit Saint Onophrius—unkempt, wearing a loincloth of leaves—with great realism: dirty fingernails, hollowed cheeks, flesh sagging from his emaciated frame. The monochromatic palette reinforces the subject’s asceticism and piety. In the foreground, the skull is a memento mori, or symbolic reminder of human mortality, an additional admonishment to the devout viewer.

Source