Musnad Ahmad Hadith 5357

It is narrated from Ibn Umar (may Allah be pleased with them both) that the Prophet (ﷺ) used to say: "Every Muslim is a brother to another Muslim; he does not oppress him nor does he disgrace him." And he used to say: "By the One in Whose hand is the soul of Muhammad (ﷺ), whenever two people love each other and then separation occurs between them, it is certainly due to the sin of one of them." And he used to say that a Muslim has six rights over his brother: to respond when he sneezes, to visit him when he is ill, to wish well for him in his absence, to greet him when they meet, to accept his invitation, and to attend his funeral when he dies. And the Prophet (ﷺ) forbade a Muslim from severing ties with his brother for more than three days.