Sisterhood in Islam is not only know someone name, but it more than that. When the love in sisterhood has been placed in the right place, there will be mutual kindness, compassion and sympathy just like one body. When one of the limbs suffers, the whole body responds to it with wakefulness and fever". They should neither deceive nor lie to each other, nor leave their sisters without assistance. They will take care each other; the honour, the blood and the property of their sisters. '' . They are like brick of a building, each strengthens the other.''  . Even this is the condition of the perfection of faith, we will never have till we wishes for our sisters what we like." 
The contract of sisterhood is a bond between two persons, like the contract of marriage between two spouses. For just as marriage gives rise to certain duties which must be fulfilled when it is entered into, so does the contract of sisterhood confer upon our sisters a certain right touching our property, our person, our tongue and our heart - by way of forgiveness, prayer, sincerity, loyalty, relief and considerateness." 
In time of Khalifah Umar Bin Khattab, there was a young man gave himself up to be judged because he killed another Moslem [in another atsar, it was an accident]. The court sentenced his crime by “Qishas” . Umar asked that man what he asked before the execution. He asked permission to go back to his homeland because He need to take care few of “amanah” [trust] and to pay some of his owes. Umar agreed with his request but with one condition, there must be someone who can guaranty him [if he didn’t back then that person would replace him to accept that punishment].
That man didn’t have relatives in Madinah, so that when he asked who wanted to guaranty him, nobody answer. But suddenly from the crowded someone yelled “I will guaranty him”. That person was Abu Dzar Al-Ghifari. Then that man was given one week to complete his matters.
In the execution day, that man still hadn’t come up. All people cried because they saw Abu Dzar was sitting in the place where the execution would be carried on. The executor was ready to execute him; he was just waiting one sign from Umar.
But suddenly there was a horse coming very fast toward that place, people heard takbir [Allahu akbar = Allah the greatest] from the rider. He was that man. He run to the execution place. At that time, he was asked “Why you come back, in fact you have chance to run away?” That man said “Yes I could just run away, But I am shy if the history would record me as a Moslem who didn’t keep his promise and didn’t take care the honor of his brother [the honor of Abu Dzar who has guaranteed him]”
The children of the victim heard that sincere answer; they felt touched by that answer then they came and said “We are the sons of the victim we decided to forgive this man” Finally that man was released from the Qishah. At that time Abu Dzar was asked “Why you want to guaranty someone that you didn’t know?” Abu Dzar answered “ I am shy if the history would record if there was an event where a Moslem asked the guaranty from his brother but no one wamted to help him” .
Then the victim’s son also were asked “Why you so that easy to forgive the murder of your dad?” They said, “We also shy the history would record record us as a Moslem who didn’t forgive their brother in Islam!”
Hudayfa radiyallahu anhu relates :
The Battle of Yarmuk had just ended. I was walking over the battle-field among the martyred and injured with a pitcher of water. I was looking for the son of my uncle.
I found him lying in blood on the burning sand. He was about to die. I asked him whether he wanted water. Unable to speak, he gestured that he did. I was just offering it to him when a groaning was heard: 'Water! Water! Please, a drop of water!'
My uncle's son, whose name was Harith, heard that and gestured that I should take the water to him. I hastened to the groaning one, who was Ikrima. Ikrima had not yet taken the pitcher when a similar groaning was heard. Refusing to take the water, Ikrima wanted me to take it to the one groaning. When I got to that one, who was 'Iyash, he was supplicating:
O God! We have never refrained from sacrificing our lives for the sake of faith. Honor us with the rank of martyrdom, and forgive our sins!
'Iyash saw the water but did not live long enough to drink it. I immediately returned to take the water to Ikrima. However, I found Ikrima also martyred. Then I hastened to Harith, my uncle's son. Unfortunately, he too was lying dead on the burning sand.
This is the most touching event I have witnessed in my life. It was their unshakable belief in Islam which caused them to behave that way. It was Islam which created such degree of brotherhood among people.
Subhanallah what’s so beautiful stories. How the bond of faith could be so that strong beyond anything – even beyond the blood connection. The sincerity to help each other unconditionally even if has to sacrifice his life. They shame if the history would record as bad person. They shame if they couldn’t help the difficulty of other brothers.
May Allah release all the hate, evil, jealousy from our heart. May Allah help us to keep only good thinkings of our sisters.....May Allah join us here for His Sake to take care each other for His sake. And then in the day of Judgment we all will be among of them who will be shade by the shade of Allah because of this love 
Subhanakallahumma wabihamdika ashadu ala ilaha illa anta astaghfiruka wa atubu ilaika
Bandung 13 Nov 2005
 Qur’an Al Hujurat 49:10
 Al-Bukhari and Muslim
 At Tirmidhi
 Al-Bukhari and Muslim
 The saying of Imam Al Ghazali
 The punishment for murder in Islam is also death except the family of the victim forgive him, he only need to pay some amount of money, this is to show how islam respect the soul human being. Qur’an Al Baqarah 2:178-179
 This is one of the touching story that I ever read [I write it with free style] until now I haven’t found the clear reference where the origin of that story, just read it from many sources....
 The story that we can find in shirah.
 HR Bukhari and HR Muslim