This is the "A Youthful Saint Reading" painted in the Italian north by Girolamo da Santacroce. The painting shows a young saint standing high on a parapet, set against a vast expanse of sky. He's dressed in green and red, reading from a book, and below him, you can see a grassy landscape with a small tower peeking through the trees and a weary traveller resting on his pack by the road.
The artist's style here is reminiscent of Giovanni Bellini's late work, particularly in the contemplative mood of the painting, the treatment of the drapery, and the rich colour palette. In fact, Girolamo da Santacroce may have even worked as an assistant to Bellini himself around 1507.
This panel would likely have been part of a larger altarpiece, possibly a polyptych, but by this time, it was becoming more common in Venice to include all the holy figures together in one unified composition. This painting is thought to have been made probably between 1512 and 1525.
A Youthful Saint Reading hangs in The National Gallery on Trafalgar Square, London — free to enter. Point your phone at any artwork there and audioguide.london plays a free audio guide in six languages — no app download needed.