Musnad Abu Ya'la al-Mawsili 3:175

Hannad ibn al-Sari narrated to us, Abu al-Ahwas narrated to us, from Abu Ishaq, from al-Harith, from Ali, who said: The Messenger of Allah (may Allah bless him and grant him peace) said: "The Muslim has six [rights] over the Muslim, [to be fulfilled] with kindness: He greets him when he meets him, he answers him when he calls him, he says 'Yarhamuk Allah' (may Allah have mercy on you) to him when he sneezes, he visits him when he is sick, he follows his funeral when he dies, and he loves for him what he loves for himself."