Abu Hurairah(R.A.)  reports that Rasulullah(Sallallaahu alaiyhi wassallam) said, “On the Day of Qiyaamah, Allah Ta’ala will announce: O son of Aadam, I was sick yet you did not visit me. He will reply, ‘O Allah, how could I have visited You since you are Rabbul ‘aalameen?  Allah Ta’ala will say: Did you not know that so and so slave of mine was sick, and yet you did not visit him? Should you have visited him you would have found Me by him. ” (Sahih Muslim)

Al-Tirmidhi (969) narrated that ‘Ali (may Allaah be pleased with him) said: I heard the Messenger of Allaah (peace and blessings of Allaah be upon him) say: “There is no Muslim who visits a (sick) Muslim early in the morning but seventy thousand angels send blessings upon him until evening comes, and if he visits him in the evening, seventy thousand angels send blessings upon him until morning comes, and he will have a garden in Paradise.” Classed as saheeh by al-Albaani in Saheeh al-Tirmidhi.

Imam Ahmad narrated that Jaabir (may Allaah be pleased with him) said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Whoever visits a sick person is plunging into mercy until he sits down, and when he sits down he is submerged in it.” Classed as saheeh by al-Albaani in al-Silsilah al-Saheehah, 2504.

According to al-Tirmidhi (2008), the Messenger of Allaah (peace and blessings of Allaah be upon him) said: “Whoever visits a sick person or visits a brother in Islam, a caller cries out to him: ‘May you be happy, may your walking be blessed, and may you occupy a dignified position in Paradise’.” Classed as hasan by al-Albaani in Saheeh al-Tirmidhi.
The Rights of one muslims on his brother are returning greetings of salaam, visiting the sick, accepting invitations, saying “yarhamuk Allaah (may Allaah have mercy on you) to a Muslim when he sneezes, and attending his funeral. The Prophet (peace and blessings of Allaah be upon him) said: “The rights of one Muslim over another are five: returning the greeting of salaam, saying ‘yarhamuk Allaah (may Allaah have mercy on you)’ when he sneezes, accepting invitations, visiting the sick and attending funerals.” (Narrated by Muslim, 2625)

‘Nuff Said