John bin Huwai
John bin Huwai was a Christian that was martyred on Muharram 10, 60 AH (680 AD) at the Battle of Karbala alongside Imam Hussein ibn Ali. John was a former slave of Abu Dharr al-Ghifari. When Abu Dharr was exiled from Medina by Uthman ibn Affan, John went to Ali ibn Abu Taleb who invited him to stay on as his companion. When Ali was martyred John stayed with Imam Hassan and after Imam Hassan's martyrdom he moved in with Imam Hussein. When Imam Hussein left Medina John insisted on accompanying him.
Battle of Karbala
At Karbala, John could always be seen at the side of Imam Hussein. He was an old man, dark with gray curly hair. Because of his profound knowledge and pleasant manners he was greatly respected. On the night before Ashura, Imam urged John to go away to seek his safety by telling him "You have accompanied us all the way but now you may go" to that John replied "how is it fair that I benefit from your company and hospitality but abandon you in your hardship?" 
John spent the whole night of Ashura sharpening his sword. On the following day he helped in repelling the first two attacks from Yazid ibn Muawiya's army. At mid-day, after the Zuhr prayers, John came to the Imam, and stood silently. Imam Hussein looked at John and said, "John, I know you have come for my permission to go to the battlefield. You have been a good and trusted friend. I will not deny you martyrdom for Islam. Go, Allah be with you!" John smiled happily. He faced the enemy and recited a poem which said:
I am a soul willing to die for Allah,
and have a sword thirsty of the blood of his enemies
Before I die I shall fight the enemies of Allah,
with my sword and my tongue serve the grandson of his prophet 
John fought while reciting the poem. He received several mortal blows but his recitation of the poem continued. John fell from his horse, he still continued to fight with his tongue by reciting the poem. And then a few horse men moved to where he lay. John, the Abyssinian, was silenced.