Page "Pietà (Michelangelo)" Paragraph 8

Another explanation suggests that Michelangelo's treatment of the subject was influenced by his passion for Dante's Divina Commedia: so well-acquainted was he with the work that when he went to Bologna he paid for hospitality by reciting verses from it.

In Paradiso ( cantica 33 of the poem ), Saint Bernard, in a prayer for the Virgin Mary, says " Vergine madre, figlia del tuo figlio " ( Virgin mother, daughter of your son ).

This is said because, being that Christ is one of the three figures of Trinity, Mary would be his daughter, but it is also she who bore him.