Pope Francis has said priests should not be priests if they cannot show mercy.

Speaking at a Mass at the Vatican yesterday, Francis said that being merciful is crucial for a priest entering a confessional box.

"If you are a priest and you can't manage to be merciful, tell your bishop who will give you a job in administration but please don't go into the confessional box! A priest who is not merciful does a lot of harm in the confessional box! He beats people."

He advised priests not to hear confession when they are stressed.

"Before going to hear Confessions, go to your doctor who will give you some pills to make you less stressed! But show mercy! And also show mercy among ourselves."

He highlighted the importance of forgiveness for priests and laypeople.

"You may be a good man, a good woman...but you are not doing what our Lord did. What's more, if you can't forgive, you cannot receive the peace of the Lord."

He said the significance of forgiveness is more than the words one says in the Lord's Prayer.

"We are trying to 'convince' God that we're good, that we're good by forgiving: in reverse. [It's just] words, right? As that beautiful song went: 'Words, words, words,' wasn't it? I think it was [the Italian singer] Mina who sung it. Words! Forgive one another! Just as the Lord has forgiven us, you do likewise."