The Pope had been asked by a 12-year-old girl why God allows children to fall victim to prostitution and drug addiction
Photos show Pope Francis holding an enormous open-air mass in the Philippine capital of Manila, attended by 4 million people.
The huge crowd is believed to be bigger than the entire population of Wales - braved pouring rain to see the Pontiff as he led a service in the city's Rizal Park.
The 78-year-old Pope, who has been on a week-long tour of Asia, wore a yellow poncho over his white cassock in an attempt to stay dry as he was driven through hundreds of thousands of worshipers on a popemobile adapted from a jeepney - the most popular mode of transport in the Phillippines.
Earlier in the day, the Pope had been asked by a 12-year-old girl why God allows children to fall victim to prostitution and drug addiction.
Glyzelle Iris Palomar broke down in tears as she said: "Many children are abandoned by their parents. Many of them became victims and bad things have happened to them, like drug addiction and prostitution. Why does God allow this to happen, even if the children are not at fault? Why is it that only a few people help us?"
The Pope hugged her and put aside most of his own prepared speech to respond.
Visibly moved, he said: "She is the only one who has put forward a question for which there is no answer and she was not even able to express it in words but rather in tears. Why do children suffer?
"I invite each one of you to ask yourselves, 'Have I learned how to weep ... when I see a hungry child, a child on the street who uses drugs, a homeless child, an abandoned child, an abused child, a child that society uses as a slave'?"
Later at the Mass, he added: "We need to see each child as a gift to be welcomed, cherished and protected. And we need to care for our young people, not allowing them to be robbed of hope and condemned to life on the streets."