The first three terraces of Purgatory relate to sins caused by a perverted love directed towards actual harm of others.
The first of the sins is pride. On the terrace where proud souls purge their sin, Dante and Virgil see beautiful sculptures expressing humility, the opposite virtue. The first example is of the Annunciation to the Virgin Mary, where she responds to the angel Gabriel with the words Ecce ancilla Dei ("Behold the handmaid of the Lord," Luke 1:38). An example of humility from classical history is the Emperor Trajan, who, according to a medieval legend, once stopped his journey to render justice to a poor widow (Canto X).
Also associated with humility is an expanded version of the Lord's Prayer:
After being introduced to humility, Dante and Virgil meet the souls of the proud, who are bent over by the weight of huge stones on their backs. As they walk around the terrace, they are able to profit from the sculpted examples of humility. The first of these souls is Omberto Aldobrandeschi, whose pride lies in his descent ("I was Italian, son of a great Tuscan: / my father was Guiglielmo Aldobrandesco"), although he is learning to be more humble ("I / do not know if you have heard his name"). Oderisi of Gubbio is an example of pride in achievements – he was a noted artist of illuminated manuscripts.Provenzano Salvani, leader of the Sienese Ghibellines, is an example of pride in dominating others(Canto XI).
In Canto XIII, Dante points out, with "frank self-awareness," that pride is also a serious flaw of his own:
After his conversations with the proud, Dante notes further sculptures on the pavement below, this time illustrating pride itself. The sculptures show Satan (Lucifer), the building of the Tower of Babel, KingSaul, Niobe, Arachne, King Rehoboam, and others.
As the poets ascend to the next terrace, an angel brushes Dante's forehead with his wings, erasing the letter "P" (peccatum) corresponding to the sin of pride, and Dante hears the beatitude Beati pauperes spiritu ("Blessed are the poor in spirit," Matthew 5:3
Enormous Loads of the Proud
The Proud Under Their Enormous Loads
William Blake Illustrations of Dante
This from Ciardi's summary:
Classics and the Western Canon discussion
The gate closes behind them and the Poets begin the ascent to The FIRST CORNICE through a tortuous passage that Dante describes as a NEEDLE’S EYE. They reach the Cornice about 9:00 or 10:00 of Monday morning.
At first the Cornice seems deserted. Dante’s eye is caught by a series of three marvelously wrought bas-reliefs in the marble of the inner cliff face. Three panels depict three scenes that serve as THE WHIP OF PRIDE, exemplifying to each sinner as he enters how far greater souls have put by far greater reasons for pride in order to pursue the grace of humility.
As Dante stands in admiration before the carvings, Virgil calls his attention to a band of souls approaching from the left, and Dante turns for his first sight of the souls of THE PROUD, who crawl agonizingly round and round the Cornice under the crushing weight of enormous slabs of rock. Their punishment is so simple and so terrible that Dante can scarcely bear to describe it. He cries out in anguish to the proud of this world to take heed of the nature of their sin and of its unbearable punishment.