Pope Francis has granted a "plenary indulgence" for those taking part.
In Catholic doctrine an indulgence frees you from being punished for your previously committed sins or it can be passed on to dead relatives to shorten their time in purgatory.
Even those following events on TV and radio can achieve a partial indulgence as long as they recite the Our Father, the Creed and other devout prayers.
Martin Luther's opposition to the sale of indulgences was one of the main causes of the Protestant Reformation in the 16th Century.
The Sacred Apostolic Penitentiary, the Vatican body dealing with forgiveness of sins, said pilgrims would have to attend confession and Mass, pray for the Pope's intentions and participate in some function during the five-day event. BBC.
