Cardinal Robert Sarah, president of the Pontifical Council Cor Unum, center, Jeannette Toure, an auditor from Ivory Coast, and bishops leave the concluding session of the extraordinary Synod of Bishops on the family at the Vatican Oct. 18. (CNS photo/Paul Haring) See SYNOD-MESSAGES and SYNOD-CONCLUSION Oct. 18, 2014.
Cardinal Robert Sarah, Prefect of the Congregation for Divine Worship and the Discipline of the Sacraments, center, and other bishops leave the concluding session of the extraordinary Synod of Bishops on the family at the Vatican in this Oct. 18, 2014 file photo. Cardinal Sarah delivered the keynote address at the World Meeting of Families Sept. 23. (CNS photo/Paul Haring)

PHILADELPHIA — Cardinal Robert Sarah had a message for the thousands of Catholics attending the World Meeting of Families: love to the end is possible.

We’re living in a world that has forgotten God, he said, and where the light of faith is in danger of being snuffed out entirely. In the midst of this darkness, Christian families are called to bring their witness of love and fidelity, thereby evangelizing the world.

Prefect of the Congregation for Divine Worship and the Discipline of the Sacraments, Cardinal Sarah of Guinea spoke of the reality of sin and the need for repentance. “Even members of the Church can be tempted to soften Christ’s teaching on marriage and family,” he said. “In front of the tragedy of sin, God puts a limit. He intervenes with His Son and His Spirit.”

We must first recognize the roots of sin in our own hearts and then repent so that we can accept the mercy of God, Cardinal Sarah said. “This is the most important good news of Christ: mercy. What a grace it is for the Church and for all of humanity that Pope Francis has called for a Year of Mercy.”

The Holy Spirit, Cardinal Sarah said, empowers us to love to the end, and gives us the faith to “overcome all that seems impossible in the family … an openness to life and faithfulness to marriage for better or for worse … forgiving the one who injures.”

It is this loving to the end that overcomes every darkness in family life — we pass from death to life through the Holy Spirit, he said. The family and every Christian is called to make this love to the end visible, thus calling others to believe, Cardinal Sarah said.

It is in the family where we learn to love and relate, where selfishness is overcome and the love of God is made real and becomes the center of our lives.

At several points in his keynote address, the audience burst into applause. “All those wounded by personal sin and the sin of others … the divorced and separated … can and must find in the Church a means of regeneration without fear of being pointed out,” he said.

Cardinal Sarah closed his address by highlighting the story of a family with 10 children that lived their faith in a dynamic way. The father was a firefighter who was killed on 9/11. Jean, the mother, said in an interview that the terrorist attacks were a great evil, but that the love of God was greater and that “God works for the good of those who love Him.” She said she prayed that God would forgive the terrorists.

Two years ago, Jean died from cancer and her eight sons carried her casket into the church. People noticed that the  15-year-old daughter, Maggie, seemed to have great peace. She told them that she knew her mother was in heaven and was experiencing perfect joy. “What more could I want for her?” she told people. The eldest son, Anthony, will soon be ordained to the priesthood.

“This is how God has worked from the beginning of creation,” Cardinal Sarah said. “God overcomes evil with good.”

Follow Joyce Coronel on Twitter at @JoyceCoronel.