This Renaissance painting is The Circumcision of Christ by Francesco Bissolo, and according to The Museum of Hoaxes, the subject was a very popular one:
The Holy Foreskin first made an appearance in medieval Europe around 800 ad, when King Charlemagne presented it as a gift to Pope Leo III. Charlemagne said it had been given to him by an angel.
However, rival foreskins soon began to pop up all over Europe. All told, twenty-one different churches claimed to have the Holy Foreskin, often at the same time...
Given the glut of Holy Foreskins, churches made efforts to have their foreskin authenticated by Church leaders as the sole genuine article...
[much internecine wrangling until...]
[The Catholic Church] adopted the view that all the rival foreskins were frauds, and in 1900 made it a crime punishable by excommunication to write or speak about the Holy Foreskin.
You must go read it all to see a seriously bothered-looking baby, to discover the fraudulent foreskin's miraculous powers, and find out which astronomical body a 17th-century theologian thought it might have ascended to become.