Pope Francis opened the huge bronze Holy Door in St. Peter's Basilica during the launch of the Jubilee Year of Mercy to welcome Catholics in the "gates of justice."
BBC reports tens of thousands of people flocked at the Mass held in St. Peter's Square on Wednesday to begin the celebration themed "revolution of tenderness."
In this Year of Mercy, the Pope called out parish priests around the world to grant absolution to repentant women who are asking for forgiveness for committing the grave sin of abortion. The Pontiff wishes to revolutionize the Church's approach to become more forgiving and understanding towards those who sincerely repent.
In March, Pope Francis described the Holy Door as the "Door of Mercy, through which anyone who enters will experience the love of God who consoles, pardons and instills hope".
"The greater the sin, the greater the love the Church must express," he said.
At the end of Wednesday's Mass, The Holy Father told attending Catholics that passing through the Holy Door is a sign of taking the role of the Good Samaritan.
The celebration of the Holy Year of Mercy started on the feast of the Immaculate Conception on December 8 and will end on the Feast of Christ the King on November 20, 2016.
The last time the Holy Door was opened was during the previous Jubilee Year, as called by St. John Paul II in 2000.
The Jubilee tradition was rooted in the Old Testament where slaves and prisoners were released once in every 50 years. Although the concept died out in Judaism, Pope Boniface VIII adopted the practice for the Catholic Church in 1300.
Pilgrims congregated in Rome to take part in the celebration and to pray for indulgences.
Also present in the Mass was 88-year-old Emeritus Pope Benedict XVI whom Pope Francis embraced before opening the sacred door.
