Anas bin Malik (May Allah be pleased with him) said:
The Messenger of Allah (ﷺ) said, "Do not desert (stop talking to) one another, do not nurse hatred towards one another, do not be jealous of one another, and become as fellow brothers and slaves of Allah. It is not lawful for a Muslim to stop talking to his brother (Muslim) for more than three days."[Al-Bukhari and Muslim]
App reference: Book 18, Hadith 81
Arabic/English book reference: Book 18, Hadith 1591