The statue does not constitute a whole with the remaining elements of the sculptural decoration of the altar. It was created much later and was re-added. According to tradition, Saint John is considered the youngest of the apostles, therefore, he has been portrayed as a young man, without a beard, with a book – because he was the author of the Gospel, The Book of Revelation and three Letters.
Paulina Kluz, "St. John the Evangelist", [in:] "The Sacred Lesser Poland Heritage", 2025, source: https://sdm.upjp2.edu.pl/en/works/st-john-the-evangelist-1