Painted between 1927 and '28, Il Precursore belongs to the body of work that Sartorio dedicated to religious subjects during those years. In the foreground, but off-centre, St. John the Baptist – the Precursor – is positioned on an austere seat, without his traditional attributes or appearance. His face, concealed by a long while veil, is inspired by central European iconography, while the artist has given particular emphasis to the gesture of his extended arm, with the index finger pointing to Christ who is still wrapped in his white shroud, as if to announce his coming. As was usually the case, Sartorio constructs the painting by combining images gleaned from his pictorial vocabulary.
Displayed at the International Exhibition of Religious Art in 1950, the work entered the Vatican Museums deposits in February 1944 with a number of other works by the same artist, in order to protect them from destruction during the war. In 1948, it was acquired by the Vatican Collections as a gift of thanks from the Sartorio family.