Visiting the sick is a great mitzva, and there is no limit to or measure for this obligation. Even God Himself treats the sick and visits them.

The Sages taught: The mitzva of visiting the sick has no measure. What is the meaning of “has no measure”? Rav Yosef thought to say: There is no fixed measure for the granting of its reward. Abaye said to him: And do all other mitzvot have a fixed measure for the granting of their reward? Didn’t we learn: Be as meticulous in observance of a minor mitzva as in a major one, as you do not know the granting of reward for mitzvot? Abaye said a different explanation: Even a prominent person should pay a visit to a lowly person. Rava said: Even one hundred times a day is appropriate.

Rav Aha bar Hanina said: Anyone who visits a sick person removes from him one-sixtieth of his suffering. The Sages said to him: If so, let sixty people enter to visit him, and thereby restore him to full health. Rav Aha bar Hanina said to them: It is like the tenths of the school of Rabbi Yehuda HaNasi. [Furthermore, visiting is effective in easing the suffering only when the visitor is] the same age [as the sick person].

Ravin said that Rav said: From where is it derived that the Holy One, blessed be He, feeds a sick person? As it is stated: “The Lord will support him on his sickbed” (Psalms 41:4). And Ravin said that Rav said: From where is it derived that the Divine Presence is resting above the bed of a sick person? As it is stated: “The Lord will support him on his sickbed.”

This is also taught [in a baraita]: One who enters to visit a sick person may sit neither on the bed nor on a bench nor on a chair. Rather, he [deferentially] wraps himself in his prayer shawl and sits on the ground, because the Divine Presence rests above the bed of a sick person, as it is stated: “The Lord will support him on his sickbed.”

What is the difference between one who is dangerously ill and one who is merely ill? One who is ill suffers from a standard illness [which follows a slow pattern of development], whereas for one who is dangerously ill, the acute illness comes upon him suddenly. In the case of one suffering from a standard illness, those close to him enter to visit him immediately and those who are distant come after three days, whereas if the illness comes upon him suddenly, both these and those enter to visit him immediately. (Nedarim 39b, 40a; Jerusalem Talmud, Gittin 6:5)