The Madonna is represented as being very young for the mother of a 33-year-old son, which is not uncommon in depictions of her at the time of the Passion of Christ. Various explanations have been suggested for this. One is that her youth symbolizes her incorruptible purity, as Michelangelo himself said to his biographer and fellow sculptor Ascanio Condivi.
"Do you not know that chaste women stay fresh much more than those who are not chaste? How much more in the case of the Virgin, who had never experienced the least lascivious desire that might change her body?"[3]
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, since Christ is one of the three figures of Trinity, Mary would be his daughter, but it is also she who bore him.