The 88-year-old pontiff is gradually making more public appearances as he recovers from the biggest health crisis in his 12 years in the role.
King Charles and Queen Camilla had been due to make a formal state visit to the Vatican, but postponed their plans after doctors prescribed Francis two months of rest.
The pope's official nurse pleaded with doctors to ensure that they did not stop his treatment despite significant risks.
The artwork, believed to be the original work of Mantegna, was recently rediscovered in the Sanctuary of Pompeii.
Tradition recounts that Longinus, a Roman centurion, pierced the side of Jesus with this very spear during the crucifixion.
Pope Francis approved a new three-year Vatican reform plan, pushing forward with change despite his ongoing health battle.
The Old Syriac text specifies disciples 'rubbing it in their hands,' highlighting significant nuances in interpretation.
Vatican says Pope Francis's health is improving but he remains under close watching Rome's Gemelli hospital.
The pope has not had any new breathing crises, the Vatican announced in a handout.
Francis, 88, has been in Rome's Gemelli hospital for two weeks, after being admitted on February 14 with a severe respiratory infection that triggered other complications.