This hadeeth comes under the following chapter: IT IS FORBIDDEN FOR A MUSLIM TO HAVE ESTRANGED RELATIONS WITH THE OTHER MUSLIM BEYOND THREE DAYS WITHOUT ANY REASON OF SHARI'AH
Abu Ayyub Ansiri reported Allaah's Messenger (sallAllaahu alayhi wa sallam) as saying: It is not permissible for a Muslim to have estranged relations with his brother beyond three nights, the one turning one way and the other turning the other way when they meet; the better of the two is one who is the first to give a greeting.