This is an excerpt from Companions of the Prophet, Vol 1 - by Abdul Wahid Hamid. This is taken from the story of Sa'id ibn Aami al Jumahi, who is the first companion described in this book.
"Sa'id ibn Aamir al Jumahi was one of thousands who left for the region of Tan'im on the outskirts of Makkah at the invitation of the Quraysh leaders to witness the killing of Khubayb ib Adiy, one of the companions of the Muhammad [(saw)] whom they had captured treacherously.
With his exuberant youthfulness and strength, Sa'id jostled through the crowd until he caught up with the Quraysh leaders, men like Sufyan ibn Harb, and Safwan ibn Umayyah, who were leading the procession.
Now he could see the prisoner of the Quraysh shackled in his chains, the women and children pushing him to the place set for his death. Khubayb's death was to be in revenge for Quraysh losses in the battle of Badr.
When the assembled throng arrived with its prisoner at the appointed place, Sa'id ibn Aamir took up his position at a point directly overlooking Khubayb as he approached the wooden cross. From there he heard Khubayb's firm, but quiet voice amid the shouting of women and children.
"If you would, leave me to pray to rakaats before my death"
This the Quraysh allowed.
Sa'id looked at Khubayb as he faced the Ka'bah and prayed. How beautiful and how composed those two rakaats seemed!
Then he saw Khubayb facing the Quraysh leaders.
"By Allah, if you thought that I asked to pray out of fear of death, I would think the prayer not worth the trouble," he said.
Sa'id then saw his people set about dismembering Khubayb's body while he was yet alive, and taunting him in the process.
"Would you like Muhammad to be in your place while you go free?
With his blood flowing, he replied, "By Allah, I would not want to be safe and secure among my family while even a thorn hurts Muhammad."
People shook their fists in the air, and the shouting increased.
"Kill him. Kill him!"
Sa'id watched Khubayb lifting his eyes to the heavens above the wooden cross.
"Count them all, O Lord," he said. "Destroy them and let not a single one escape."
Thereafter Sa'id could not count the number of swords and spears which cut through Kubayb's body.
The Quraysh returned to Makkah and in the eventful days that followed forgot Khubayb and his death. But approaching manhood. Sa'id would see him in his dreams while asleep and he would picture Khubayb in front of him praying his two rakaats, calm and contented, before the wooden cross. And he would hear the reverberation of Khubayb's voice as he prayed for the punishment of the Quraysh. He would become afraid that a thunderbolt from the sky or some calamity would strike him.
Khubayb, by his death, had taught Sa'id what he did not realize before - that real life was faith, and conviction and struggle in the path of faith, even until death. He taught him also that faith which is deeply ingrained in a person works wonders and performs miracles. He taught him something else too - that the man who is loved by his companions with such a love as Khubayb's could only be a prophet with Divine Support" (p.1-p.2)
I. Love. This. Story.
I also like to point out, because this bothered me a little bit, that when the Muslims did conquer Mecca, the Prophet (saw) forgave and let the non-Muslims living in Mecca leave unharmed.
The idea of cursing someone has always struck me as being an 'absolute wrong'. As in, it is NEVER okay to ask God to harm someone. I can understand why they would make the supplication, but I definitely don't support it. I think the Prophet's actions when he conquered Mecca shows that it is also not Islam's stance either.
Also, I'm not trying to convert anyone with this story. That's just where the focus changes, and the section involving Khubayb ends.