All are called by God to return to him with their “whole heart,” said Pope Benedict XVI at a special celebration for Ash Wednesday.

The Pope led a procession across Rome's Aventine Hill for the first day of Lent. The celebration of the liturgy began at the St. Anselm's Church with members of the Benedictine order, cardinals, bishops and priests.

When they reached the singing of the litany of the saints, they began the procession that led them several hundred yards down the street to Dominican Minor Basilica of Saint Sabina. There, the Pope presided over the rest of the Mass.

Through the imposition of the ashes on the first day of Lent, “we undertake to convert our hearts to the horizons of grace,” the Pope said during his homily.

He spoke of Lent not as a time of sadness, but instead as “a precious gift of God and a time of strength and full of significance in the journey of the Church.

“It is the road to the Lord's Passover,” he said.

Pope Benedict explained that the day's readings called for full conversion, “not a superficial and transient conversion, but a spiritual journey that covers in depth the attitudes of conscience and presupposes a sincere act of repentance.”

There is a call for an attitude of genuine conversion, a return to God through the recognition of his holiness, power and majesty, he explained. “And this conversion is possible because God is rich in mercy and love.”

Converting is not only a “human task,” he explained, calling it “the movement of a contrite heart attracted and moved by grace to respond to the merciful love of God who loved us first.”

More in Vatican

The Christian witness makes believers into a “living message,” Pope Benedict said, adding that “in many cases we are the only Gospel that people today still read.”

Another reason to live Lent to the fullest is the Christian responsibility “to offer a living witness of faith in a troubled world that needs to return to God, a world which needs conversion,” he said.

The Pope closed with an additional call to Christians to live this time with trust and joy.

Lent, he said, “is a powerful time in the liturgical year, and it is a special time that is given to us to look, with greater commitment, to our conversion, to listen more attentively to the Word of God, a time for prayer and penance – of opening our hearts to the workings of Divine will, for a more generous practice of mortification, thanks to which we can be more attentive to neighbors in need.”