This unfinished panel represents St. Jerome (AD 347-420), one of the four doctors of the Western Church, in a scene inspired by the fanciful account of the Saint’s later life given in Jacobus de Voragine’s Golden Legend. St Jerome lived in the desert for four years, with, in his own words, “only the scorpions and wild beasts for company”.

Leonardo portrays the very elderly Jerome, gaunt and almost toothless, kneeling in a rocky landscape in prayerful contemplation. In his right hand he holds a stone with which he beat his breast to chastise himself. In the foreground we see the lion that was said to have become Jerome’s faithful companion after the Saint removed a thorn from its paw. In the background on the right, through what appears to be an opening of a cave, a briefly sketched church façade has been included, which is another attribute of St. Jerome and a reference to his status as father of the Church. On the upper left Leonardo has freely sketched a mountain range enveloped in a hazy atmosphere, which is not unlike the landscape of the Virgin of the Rocks.

The body of St. Jerome is a testament to Leonardo’s study and knowledge of human anatomy and movement, and his ability to convey expression through bodily form. The lifelike appearance of St. Jerome’s lion indicates Leonardo’s knowledge of nature, probably gained through the study of real lions in drawings.