Pope Francis is reminding priests to always be merciful, as he ordained 16 men in a ceremony in St. Peter's Basilica.

In remarks Sunday to the new priests from several nations, Francis said: "Please, don't tire of being merciful" since they themselves sin.

He told them to work only in service to God for the good of the faithful.

Encouragement toward mercy and selfless service is a hallmark of Francis' 5-year-old papacy.

Francis gripped a hand of each man as, one by one, they knelt before him. He asked if they promised "me, and my successors, filial respect and obedience." They each replied, "Yes, I promise."

Pedophile priests and church hierarchy's cover-up of sex abuse have stained the Catholic church's reputation and tested Francis' own ability to combat the problem.