Amr bin Murrah (may Allah have mercy on him) says: I asked Sa'id bin Jubayr (may Allah have mercy on him) about the two arbiters. He said: I did not live at that time. I said: I am only asking you about the two arbiters who are in the Book of Allah, meaning the Qur'an. He said: An arbiter is sent from his family and an arbiter from her family. They speak to one of the two and admonish him; if he comes back, well and good; otherwise they speak to the other and admonish him; if he comes back, well and good; otherwise the two arbiters give their decision, and whatever they decide is valid.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب القسم والنشوز / 14792