Allah, the Wise, has said:
كُونُوا قَوَّامِينَ لِله شُهَداَءَ بِالْقِسطِ
"Be upright for Allah, bearers of witness with justice." 
Imam A'li (a.s.) has said:
مَنْ يُنْصِفُ مِنْ نَفْسِهِ لَمْ يَزِدهُ اللهُ إلاَّ عِزًّا
"One, who exhibits fairness on his part, Allah shall increase him in glory." 
A person’s faith does not become perfect until he observes fairness with respect to himself and others. In exchange, God shall increase his honour and glory.
Man, by nature, prefers his own self and loves everything that is associated with him. He also possesses a dislike for everything bad and evil. Thus, if he helps someone in need, he would be commended by one and all. Similarly, (justice demands that) if he does not desire anything bad and evil for himself, he should not desire it for the others too.
This also holds true when mediating between two warring parties; never should he side unfairly with one, against the other, even if the outcome results in his own detriment.
1 – An Advice from the Holy Prophet (s.a.w.)
An Arab approached the Holy Prophet (s.a.w.) when he was about to embark upon a military expedition.
Seizing the reins of the Prophet’scamel, he said, "O’ Prophet of Allah! Inform me of a deed that would earn me Paradise."
"Conduct yourself with people in the same manner as you would want them to behave towards you and refrain from doing to them what you would not want them to do to you," advised the Prophet (s.a.w.) and then added, "Let go of the reins (for I have to go for jihad)."
2 – The Equity of A'li (a.s.)
Like the other youths, I entered the vast open ground of Kufah, where I witnessed Amirul Mu'mineen (a.s.) standing beside two containers which were filled with gold and silver coins. He had a small whip in his hand. A huge crowd had gathered around him and he kept them back by means of his whip, to prevent them from hampering the distribution of the money.
The Imam (a.s.) began distributing the money amongst the people until nothing remained for himself and he returned home empty-handed.
I returned home and said to my father, "I witnessed a very strange act today but I fail to comprehend if this person’s action was good or bad because he never retained anything for himself!"
My father inquired, "Who was the person?"
"Amirul Mu'mineen (a.s.)," I replied and then went on to narrate what had transpired earlier. Upon hearing A'li’s (a.s.) fairness in distributing the money, my father began to weep and said to me, "My son, you have witnessed the most excellent person from amongst the people."
3 – A’di Ibn Haatim
A’di, the son of the well-known Haatim Taai, was one of the sincere and loyal companions of Amirul Mu'mineen (a.s.). From the year 10 A.H. when he accepted Islam, A’di had always remained in the service of the Imam (a.s.), and had fought alongside him in the battles of Jamal, Siffeen and Nahrawaan. In the battle of Jamal he sustained an injury to one of his eyes as a result of which he lost his vision.
Once he came to Mua'wiyah for some purpose. Mua’wiyah asked him why he had not brought his sons with him.
"They were killed while fighting alongside Amirul Mu'mineen (a.s.)," he replied.
"A'li has not been just to you, for he sent your sons to be killed while he has kept his own sons alive!" said Mua’wiyah.
A’di retorted, "(On the contrary) I have not done justice to A’li for he has been killed, whereas I am still alive. O’ Mua'wiyah! Our rage towards you still smoulders in our hearts. Do know that (the pain of) having our throats slit or the agony of death is easier for us to bear than hearing bad comments about A'li (a.s.)."
4 – The Fairness of Abu Dharr
On the way towards the battle of Tabuk, Abu Dharr fell behind the army because he was mounted on a slow animal. When the others realized this, they notified the Holy Prophet (s.a.w.), who said:
"If he possesses goodness in him, God shall make him reach you."
Meanwhile, Abu Dharr, disappointed with his animal, dismounted and proceeded on foot. The Holy Prophet (s.a.w.) found a convenient place and had decided to pitch the tents, when one of the Muslims shouted that there was someone in the distance approaching them.
The Holy Prophet (s.a.w.) prayed:
O’ Lord! May it be Abu Dharr!
The others informed him that it was indeed Abu Dharr. The Prophet supplicated:
May Allah forgive Abu Dharr! He travels alone, shall die alone and shall be resurrected alone. He then asked the people to provide Abu Dharr with some water, as he appeared to be thirsty.
But when Abu Dharr arrived in his presence, the Prophet (s.a.w.) observed that he had a container of water in his possession, and so asked him, "Abu Dharr! You had water with you and yet you remained thirsty?"
"Yes! O’ Prophet of Allah! May my parents be sacrificed for you! On the way, I was overcome by thirst. I reached a place where there was some water. Tasting it, I found it to be cold and delicious and so said to myself: (It is not fair) if I drink this water before the Holy Prophet (s.a.w.)," replied Abu Dharr.
Hearing this, the Holy Prophet (s.a.w.) said, "O’ Abu Dharr! May Allah forgive your sins! You shall lead your life in solitude, die as a stranger, away from home, and enter Paradise alone."
 Holy Qur'an, ch. Al-Maidah (5), vs. 8.
 Jaame' al-Sa'adaat, vol. 1, pg. 368.
 Al-Kafi, vol. 2, Chapter of Fairness, tr. 10.
 Al-Ghaaraat, vol. 1, pg. 55; Dastaanhai Az Zindagi A'li, pg. 7.
 Located three hundred miles north of Medinah.
 Paighambar Wa Yaaraan, vol. 1, pg. 49; Al-Isaabah, vol. 4, pg. 65