It is narrated from Sayyiduna Abu Ayyub al-Ansari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Do not turn your backs on one another, do not cut one another off, and be, O servants of Allah, brothers. The believers' estrangement is (allowed) for three days; then if they speak to each other, well and good; otherwise Allah, the Mighty and Majestic, turns away from them both until they speak to each other."
Hadith Referenceالمعجم الكبير للطبراني / باب الخاء / 3942