It is a Sunnah of our Beloved Prophet Muhammad (pbuh) to visit the sick. We should always visit those who are sick because it helps us to reflect and take heed, as those who are ill are close to Allah Ta'ala. We have only to consider that the sick person has no one to call but Allah, nothing to reflect on but Allah, and his condition reminds us of the blessing of health.
Hadrat Abu Moosa (R.A.) reports that the Prophet (pbuh) said, 'Visit the sick, feed the hungry and free the one who is imprisoned (unjustly).' [Sahih Bukhaari]
Hadrat Abu Hurairah (R.A.) reports that the Prophet (pbuh) 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]
Hadrat Ali (R.A.) reports that the Prophet (pbuh) said, 'When a Muslim visits his sick Muslim brother in the morning, seventy thousand angels make dua for his forgiveness till the evening. And when he visits him in the evening, seventy thousand angels make dua for his forgiveness till the morning, and he will be granted a garden for it in Jannah.' [Timizi, Abu Dawood]
Hadrat Anas (R.A.) reports that the Prophet (pbuh) said, 'When a person performs a proper wudhu (observing all its etiquette) and then goes to visit his sick Muslim brother with the intention of gaining sawaab, then he will be kept far away from the Fire of Jahannam by a distance equivalent of Sixty years.' [Abu Dawood]
Our Beloved Prophet (pbuh) also said, 'Whoever visits a sick person (for the pleasure of Allah), a Caller from the skies announces: You are indeed blessed and your walking is blessed and you have (by this noble act) built yourself a home in Jannah.' [Ibn Maajah]
Hadrat Ibn Abbaas (R.A.) relates: It is part of the Sunnah that when you visit a sick person, you should shorten your visit to him and make the least amount of noise by him. [Mishkaat]
Once our Prophet (pbuh) said, 'The best type of visit to a sick person is when the visitor gets up to leave without delay.' [Bayhaqi]
If we act upon these simple teachings, then the visitors to a hospital will no longer remain a problem for those who are in charge of the administration of hospitals.
Hadrat Umm Salmah (R.A.) relates that the Prophet (pbuh) said, 'When you visit a sick person or (go to the home of) someone who has died, then speak only what is good, for the angels say 'aameen' to whatever you will say.' [Sahih Muslim]
Hadrat Abu Sa'eed Khudri (R.A.) reports that Rasulullah(Sallallaahu alaiyhi wassallam) said, 'When you visit a sick person, speak in a reassuring way to him (about his age and his life).' (For instance, tell him, 'Alhamdulillah, your health has improved' or 'Inshaa Allah you will get better soon.') Saying this will not delay what is predestined, but it will certainly make him feel happy.' [Tirmizi, Ibn Maajah]
Source: Sickness- also a Mercy from Allah