VATICAN CITY (CNS) -- Carrying the cross means more than bearing personal suffering -- it means stepping into the pain of others and walking beside them, Pope Francis wrote at the start of Holy Week.

"To carry the cross of Christ is never in vain," he wrote in his homily for Palm Sunday Mass in St. Peter's Square April 13. "It is the most tangible way for us to share in his redemptive love."

The pope, still recovering from respiratory infections, made only a brief appearance in the square at the end of Mass, but his homily was read by Argentine Cardinal Leonardo Sandri, subdean of the College of Cardinals, who celebrated the Mass.

"Have a good Palm Sunday. Have a good Holy Week," the pope said with a strained voice from the stage in St. Peter's Square. He was not using a nasal cannula to receive oxygen during his public appearance unlike the week before when he had come to the square at the end of Mass to a deliver a blessing.

The Vatican also released a video of the pope in St. Peter's Basilica after the Mass; he stopped to pray before the tombs of Sts. Peter, Pius X and his successor, Pope Benedict XV.

Despite a two-month convalescence prescribed by his doctors following his release from the hospital March 23, Pope Francis had made several surprise public appearances in the previous week.

He delivered a blessing in St. Peter's Square at the end of the Mass for the Jubilee of the Sick and Health Care Workers April 6, prayed before the newly restored tomb of Pope Urban VIII in St. Peter's Basilica April 10 while dressed in casual attire and went to the Basilica of St. Mary Major in Rome to pray April 12.

As of April 13, the Vatican had not confirmed which Holy Week liturgies the pope may attend.

The Palm Sunday Mass began with throngs of laypeople processing into St. Peter's Square holding palm branches, followed by more than 60 cardinals and bishops.

More than 20,000 people, many holding olive branches -- a Palm Sunday tradition in Italy -- listened as the Passion narrative from St. Luke's Gospel was proclaimed.

In his written homily, Pope Francis reflected on Simon of Cyrene, the man forced by Roman soldiers to carry the cross behind Jesus.

Simon, the pope said, did not speak but simply acted, and in doing so became part of salvation history. "Between him and Jesus, there is no dialogue; not a single word is spoken. Between him and Jesus, there is only the wood of the cross."

Pope Francis invited Christians to reflect on how they respond to the suffering of others -- with "anger or pity, compassion or annoyance" -- and to recognize Christ in the people whose lives are burdened by pain and injustice.

"How many Simons of Cyrene are there in our own day, bearing the cross of Christ on their shoulders!" he wrote. "Can we recognize them? Can we see the Lord in their faces, marred by the burden of war and deprivation?"

Recognizing those faces, the pope said, must move believers to action.

"Jesus' passion becomes compassion whenever we hold out our hand to those who feel they cannot go on, when we lift up those who have fallen, when we embrace those who are discouraged," he said.

At the start of Holy Week, Pope Francis called on Christians to prepare for Easter by becoming companions to one another on the road of suffering and mercy.

"In order to experience this great miracle of mercy, let us decide how we are meant to carry our own cross during this Holy Week: if not on our shoulders, in our hearts," the pope wrote. "And not only our cross, but also the cross of those who suffer all around us."

"Let us prepare for the Lord's paschal mystery," he said, "by becoming each of us, for one another, a Simon of Cyrene."

In his message for the recitation of the Angelus, published by the Vatican, the pope thanked people for their prayers during his illness and asked them to join him in praying for those suffering from war, poverty and natural disasters. He made a particular appeal for peace in Sudan, where April 15 marks two years since the outbreak of civil war, and remembered the victims of a building collapse in Santo Domingo, Dominican Republic.

"May peace finally come to martyred Ukraine, to Palestine, Israel, the Democratic Republic of Congo, Myanmar and South Sudan," he wrote. "Mary, Our Lady of Sorrows, obtain this grace for us and help us to live Holy Week with faith."