Al Bukhari reported in Al Adab Al Mufrad on the authority of Sa`id ibn Wahb who said: I was with Salman when he visited a sick person in Kinda. When he went in, he said: Good news! Allah makes the illness of the believer an expiation for him and a restoration, whereas the illness of the corrupt person is like a camel whose people hobble it and then let it go. It does not know why it was hobbled or released." [Al Adab Al Mufrad No. 493, and Al Albany graded it as authentic. in Sahih Al Adab No. 379].
The Prophet gave him glad tidings and reminded him that calamities that hit a Muslim in his body are all expiations for his sins as was reported in Sahih Al Bukhari and Sahih Muslim from the Hadith of Abu Hurayrah (may Allah be pleased with him) who narrated that the Prophet (peace be upon him) said: "No fatigue, nor disease, nor sorrow, nor sadness, nor hurt, nor distress befalls a Muslim, even if it were the prick he receives from a thorn, but that Allah expiates some of his sins for that." [Sahih Al Bukhari No. 5642, and Sahih Muslim No. 2573].
As for the Prophet's saying: "restoration," i.e., during his sickness a person recalls his sins, mistakes, and negligence which he does not recall during his health, at that time his sickness shall be a cause for blaming himself for negligence and a motive for abandoning bad things and asking for Allah's Pleasures. However, as for the disbeliever, when he gets sick, he becomes like a camel whose owner tied then released without knowing why it was tied or why it was released because he continues doing his mistakes and sins without taking a lesson from his sickness.
A person who visits the sick should choose a proper time for visiting because the meaning of visiting is adding comfort to the sick not to trouble him. Therefore, a visitor should not stay long with the sick except the sick loves that or his long stay contains a benefit for the sick.
It is part of the Sunnah that a visitor sits at the head of the sick. It was reported in Al Adab Al Mufrad of Imam Al Bukhari (may Allah be merciful with his soul) on the authority of Ibn `Abbas (may Allah be pleased with him) who said: "When the Prophet (peace be upon him) visited a sick person, he would sit at his head and then say seven times: I ask Allah the Immense, the Lord of the Immense Throne, to cure you. If the time of his death had not yet come, he would be cured of his pain." [Al Adab Al Mufrad No. 536, and Al Albany (may Allah bestow mercy on his soul) graded it as authentic in Sahih Al Adab No. 416].
It is part of the Sunnah that a visitor puts his hand on the body of the sick when he wants to invoke Allah for him. It was reported in Sahih Al Bukhari and Sahih Muslim: When the Messenger of Allah (peace be upon him) visited Sa`d ibn Abu Waqqas (may Allah be pleased with him), he placed his hand on his forehead then placed his hand on his face and belly and said: "O Allah, cure Sa`d." [Sahih Al Bukhari No. 5659 and Sahih Muslim No. 1628]. Placing the hand on the face and belly can show the weakness or power of the sickness, as it is a comfort for the sick.
A visitor should invoke Allah for the sick and does not say but nice words in his presence. It was reported in Sahih Al Bukhari and Sahih Muslim on the authority of Um Salamah (may Allah be pleased with her) who said that the Prophet (peace be upon him) said: "Whenever you visit the sick or the dead, supplicate for goodness because angels say: Amen to whatever you say." [Sahih Muslim No. 919].
A visitor should select the most inclusive invocations, especially those reported from the Prophet (peace be upon him) because they are blessed, inclusive, and are not erroneous such as to say: "O Allah, cure so and so." Or to say: "Purification if Allah wills." Or to say: "I ask Allah, the Great, the Lord of the Great Throne to cure you." Or to say: "O Allah, the Lord of the people! Remove the trouble, cure him, for You are the One who is able to cure, there is no cure but Yours: It is a cure without having any side effects." A visitor may also invoke Allah with Surat Al Fatihah or Surat An-Nas and Surat Al Falaq because of the Hadith of Abu Sa`id Al Khudry and the Hadith of `A'ishah which we have mentioned. A visitor may also say: "In the name of Allah, I protect you from everything and safeguard you from every evil that may harm you and from the eye of a jealous one. Allah would cure you and I invoke the name of Allah for you" as Gabriel cured the Prophet (peace be upon him) when he was sick. A person may say as was reported in Sahih Al Bukhari and Sahih Muslim on the authority of `A'ishah (may Allah be pleased with her) who said that the Prophet (peace be upon him) used to say when visiting the sick: "In the Name of Allah, by the earth of our land and the saliva of some of us, may Allah cure our patient [The prophet was putting his finger in his mouth [to take some of his blessed saliva] then put it in earth [to take the blessing on the Medina ground] and put it on the wound]." [Sahih Al Bukhari No. 5745 and Sahih Muslim No. 2194].
A visitor should take a lesson when he visits the sick, praise Allah for good health and safety, and to ask Him for good health.
We ask Allah, the Most Generous to cure our sick and the Muslim sick, and to grant us all good health and safety, for He is All Hearing, All Responding.