Volume 3, Book 49, Number 858 :
Narrated by Sahl bin Sad (radiallaahu `anhu)
Once the people of Quba fought with each other till they threw stones on each other. When Allah’s Apostle (sallallaahu `alayhi wasallam) was informed about it, he said, “Let us go to bring about a reconciliation between them.”
Prophet (sallallaahu `alayhi wasallam) was the leader, head of state. It was part of his job to keep peace among people. As soon as he heard about the fight, he instantly wanted to set off to help clear the matter.. and it seems like he took others along with him, as if preparing them for future responsibilities.
Reconciling between people is an important issue in Islam, one which brings a great deal of reward. There is also a stern warning against sewing discord between people. Because of the importance of reconciling people in the Muslim society and the seriousness of discord and conflict, Allaah has permitted lying in order to reconcile between people and to remove discord and conflict which may have negative consequences for the religious commitment of individuals and communities.
It was narrated from Abu’l-Darda’ (may Allaah be pleased with him) that the Prophet (peace and blessings of Allaah be upon him) said: “Shall I not tell you of something that is better than fasting, prayer and charity?” They said: Yes. He said: “Reconciling between two people, for discord between people is the shaver.” Narrated by al-Tirmidhi, who said: this is a hasan hadeeth. And it is narrated that the Prophet (peace and blessings of Allaah be upon him) said: “It is the shaver, and I do not say that it shaves hair, rather that it shaves religious commitment.” End quote.
Whomsoever Allaah honours and enables him to reconcile between Muslims, if he needs to tell lies in order to reconcile between them, there is no sin on him for that, and it is not permissible to describe him as a liar, because the matter is serious; it is the matter of shar’i interests which means that in this case, lying is permissible, as it is narrated in al-Saheehayn from the hadeeth of Umm Kalthoom bint ‘Uqbah (may Allaah be pleased with her) that she heard the Prophet (peace and blessings of Allaah be upon him) say: “He is not a liar who reconciles between people, conveying good messages and saying good things.” Narrated by al-Bukhaari, 2546; Muslim, 2605
Taken from IslamQA