VATICAN CITY — Love for those society considers “useless” or even a bother led St. Teresa of Calcutta to a courageous defense of the unborn, said Cardinal Pietro Parolin.

Like prophets and saints before her, Mother Teresa would not “kneel down before anyone but the Almighty” and would not bow before “the fashions or idols of the moment,” said Parolin, the Vatican Secretary of State.

On the 19th anniversary of Mother Teresa’s death, Sept. 5 — her feast day — the cardinal presided over a Mass in St. Peter’s Square to give thanks for the canonization of the founder of the Missionaries of Charity.

With hundreds of Missionaries of Charity gathered on the steps of St. Peter’s Basilica and several thousand pilgrims in the square, Parolin held Mother Teresa up as “a gleaming mirror of God’s love and a marvelous example of service to one’s neighbor.”

Her example, the cardinal said, is a call to all Christians “to convert from being lukewarm and mediocre to allow ourselves to be set alight by the fire of Christ’s love.”

While Mother Teresa became famous for her care of the poorest of the materially poor, he said she knew the worst form of poverty was to be unloved and unwanted.

“That led her to identify as ‘the poorest of the poor’ children who were not yet born and whose existence was threatened,” Cardinal Parolin said. “An unborn baby has nothing of its own; its every hope and need is in the hands of another.”

The unborn, he said, “ask to be welcomed and protected so they can become what they already are: one of us.”

Like every human being, the cardinal said, the unborn have one basic mission in life: “to love and be loved, as Mother Teresa liked to say.”

“The heroic exercise of charity and the clear proclamation of truth” were found in Mother Teresa, he said.

At the end of the Mass, Missionaries of Charity Father Brian Kolodiejchuk thanked Pope Francis for canonizing Mother Teresa. The priest served as postulator or chief promoter of her sainthood cause.

“We really cannot thank God enough for all he has done for us through St. Teresa,” he told those in the square. “Following her example of faith and love, may we even more generously and faithfully love God with all our hearts and see and love God in our neighbors, especially the most unloved, unwanted and uncared for of our brothers and sisters.”

Recognizing all those involved in making the celebration of her sainthood a joyful and prayerful experience, he also said, “We thank the poorest of the poor in whom Jesus is loved and served.”