VATICAN CITY -- The Catholic Church's current Synod of Bishops should not be a "parliament for demanding rights," but a "journey in accordance with the Spirit," Pope Francis said.

The synod, which seeks to gather input from all baptized Catholics on building a listening church, is not "an occasion for following wherever the wind is blowing, but the opportunity to submit to the breath of the Spirit," he said.

In his homily for Pentecost Mass in St. Peter's Basilica May 28, the pope said that the Holy Spirit is "the heart of synodality and the driving force of evangelization."

"Without him, the church is lifeless, faith is mere doctrine, morality only a duty" and "pastoral work mere toil," he said. "We often hear so many so-called thinkers and theologians who give us cold doctrines that seem mathematical because they lack the Spirit."

Pope Francis, seated to the side of the basilica's main altar, spoke without difficulty just two days after he had cleared his day's schedule due to a fever.

Brazilian Cardinal João Braz de Aviz, prefect of the Dicastery for Institutes of Consecrated Life and Societies of Apostolic Life, was the main celebrant at the altar alongside Cardinals Giovanni Battista Re, dean of the College of Cardinals, and Leonardo Sandri, vice dean.

Reflecting on St. John's account of Jesus breathing on the apostles to impart the Holy Spirit, Pope Francis urged Christians to seek harmony in the church without doing away with the differences that enrich its character.

"The Spirit does not inaugurate the church by providing the community with rules and regulations, but by descending upon each of the apostles, every one of them receives particular graces and charisms," he explained. The Spirit "does not eliminate differences of cultures but harmonizes everything without reducing them to bland uniformity."

Embracing difference, the pope said, is key to resisting the temptation to look back in time with nostalgia or become "caught up in our plans and projects."

At Pentecost, however, "the life of the church began not from a precise and detailed plan, but from the shared experience of God's love," he said.

Pope Francis asked Christians to invoke the Holy Spirit daily to create harmony where there is division in the church and beyond.

"Let us think of the wars, so many conflicts, it seems incredible the evil of which we are capable. Yet fueling our hostilities is the spirit of division, the devil, whose very name means 'divider,'" he said.

Conversely, the Holy Spirit "opposes the spirit of division because he is harmony, the Spirit of unity, the bringer of peace."

"If the world is divided, if the church is polarized, if hearts are broken, let us not waste time in criticizing others and growing angry with one another," Pope Francis said, "instead, let us invoke the Holy Spirit."

The pope encouraged Christians to reflect on their relationship with the Holy Spirit and asked them to develop a faith that is "docile in the Spirit," and not "stubbornly attached" to "so-called doctrines that are only cold expressions of life."

"If we want harmony let us seek (the Spirit), not worldly substitutes," he said.

At the end of Mass, Pope Francis he smiled and waved to onlookers as he was taken down the basilica's central nave while seated in a wheelchair.

Reciting the "Regina Coeli" prayer with an estimated 15,000 people gathered in St. Peter's Square after the Mass, Pope Francis again spoke of the synod, asking people to join special prayers planned for May 31, the end of the month traditionally dedicated to Mary.

"At the conclusion of the month of May," he said, "Marian shrines around the world are planning moments of prayer to support preparations for the upcoming ordinary assembly of the Synod of Bishops," which is scheduled to meet in October at the Vatican. "We ask the Virgin Mary to accompany this important stage of the synod with her maternal protection."

"And to her we also entrust the desire for peace of so many peoples throughout the world, especially of the tormented Ukraine," he said.