Members of the assembly of the Synod of Bishops are not gathered in Rome to implement a "plan of reformation" but to walk together as a church that discerns God's will for the present moment, Pope Francis said at the assembly's opening Mass.

With cardinals from across the world at his side, including 20 new cardinals from 16 nations created just four days prior, the pope urged people to avoid looking at the synod through the lens of "human strategies, political calculations or ideological battles."

Asking "whether the synod will give this or that permission, open this or that door, this is not useful," he said at the Mass Oct. 4 in St. Peter's Square.

Instead, Pope Francis said the primary task of the synod is to "refocus our gaze on God, to be a church that looks mercifully at humanity, a church that is united and fraternal -- or at least tries to be united and fraternal."

The pope acknowledged that some people have fears about the synod, but he asked them to remember that it is "not a political gathering, but a convocation in the Spirit; not a polarized parliament, but a place of grace and communion."

"The Holy Spirit often shatters our expectations to create something new that surpasses our predictions and negativity," he said.

Through "synodal dialogue," the pope said, "we can grow in unity and friendship with the Lord in order to look at today's challenges with his gaze," becoming a church "which does not impose burdens" and is "open to everyone, everyone, everyone."

"The blessing and welcoming gaze of Jesus prevents us from falling into some dangerous temptations: of being a rigid church -- a customs office -- which arms itself against the world and looks backward; of being a lukewarm church which surrenders to the fashions of the world; of being a tired church, turned in on itself," he said.

Lay members and ecumenical delegates to the assembly of the Synod of Bishops led the procession into St. Peter's Square -- still decorated with flowers from the consistory that created 21 new cardinals Sep. 30 -- followed by priests, bishops and then cardinals. Synod members had participated in a retreat outside Rome Oct. 1-3, during which they reflected on ways to overcome differences of opinion and to listen to each other and to the Holy Spirit.

Cardinal Giovanni Battista Re was the main celebrant at the altar for the Mass; Cardinals Mario Grech, synod secretary-general, and Robert Prevost, prefect of the Dicastery for Bishops, one of the new cardinals, joined him at the altar. The Vatican said some 25,000 people were present in St. Peter's Square.

Celebrating the Mass on the feast of St. Francis of Assisi, a day when Pope Francis also published an apostolic exhortation on the environment, he recalled the story that Jesus told the medieval saint to "repair my church."

"The synod serves to remind us of this: our mother the church is always in need of purification, of being repaired, for we are a people made up of forgiven sinners," he said.

St. Francis lived in a time of "struggles and divisions between temporal and religious powers, between the institutional church and heretical currents, between Christians and other believers," Pope Francis said. But the saint "did not criticize or lash out at anyone." Rather, he took up the "weapons of the Gospel: humility and unity, prayer and charity."

"Let us do the same!" urged the pope, noting that the "most fruitful moments of the synod are the moments and prayer and the environment of prayer in which the Lord acts in us."

After the Mass, Pope Francis individually greeted the 20 new cardinals with him on stage, some of whom will remain in Rome to participate in the synod assembly while others were to return to their dioceses. Cardinal Luis Pascual Dri, a 96-year-old Capuchin friar from Argentina, did not travel to Rome to receive his red hat because of his health.