Baba Metzia 30b — Whoever visits the sick removes one sixtieth of his illness, while one who ignores a sick person hastens his death.
Nedarim 39b-40a — Rabbi Helbo fell sick and no one visited him. Rabbi Kahana rebuked the sages: Did it not once happen, he reminded them, that one of Rabbi Akiva\'s disciples fell sick and the sages did not visit him? So Rabbi Akiva himself visited him and because [he arranged to have the floor] swept and washed, the sick man recovered. My master, [the sick man] said [to Rabbi Akiva], you have revived me. Rabbi Akiva went out and taught, He who does not visit the sick is like a shedder of blood.
Nedarim 40a — He who visits the sick will be spared the punishments of the next world.
Rambam Hilchot Avel 14:4 — Whoever visits the sick, it is as if he removes part of his sickness and makes it easier on him, while one who ignores a sick person is like one who sheds blood.