It is narrated from Sayyiduna Abu Ayyub Ansari (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) said: "It is not permissible for anyone to shun his brother for more than three nights, such that when they meet, this one turns away and that one turns away as well. And the better of the two is the one who initiates the greeting of peace (salam)."
Hadith Referenceالادب المفرد / كتاب / 399
Hadith Gradingالألبانی:صحيح
Hadith Takhrij«صحيح : أخرجه البخاري ، كتاب الأدب : 6077 و مسلم : 2560 و أبوداؤد : 4911 و الترمذي : 1932 - انظر الصحيحة : 1246»
Explanation & Benefits
Shaykh Maulana Usman Muneeb
Benefits and Issues: After displeasure, taking the initiative to greet (with salam) is a difficult task, but it is very great. Through this, the pleasure of Allah is attained. Prolonged estrangement from one another leads to malice and enmity, and a person remains constantly involved in dangerous sins such as backbiting and envy. Therefore, before displeasure turns into rancor, it should be ended.
Source: Fadlullah al-Ahad: Urdu Commentary on al-Adab al-Mufrad, Page: 399