The mother, being so holy, could possibly be object of an attack by Satan.

Henry D'souza
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So I said let's do the prayer of exorcism over her. So I called one of the priests who was a holy man in Calcutta, ... I told him, 'Please say the prayer of exorcism over Mother Teresa.' And he got a shock and said, 'Shall I pray and should I drive out the devil if it's there?'

Henry D'souza
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I said, 'Yes, you do.' But he says, 'What will the devil do to me?' I said to him, 'You command the devil to go if he's there. In the name of the church, as archbishop, I command you to go and do it.' -Henry D'souza
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