Gemara

(Beraisa): There is no measure to Bikur Cholim.

Question: In what sense is it unlimited?

Answer #1 (Rav Yosef): There is no limit to its reward.

Objection (Abaye): The reward of all Mitzvos is unlimited!

(Mishnah): Be as careful about a light Mitzvah as about a severe one, for you do not know the reward of Mitzvos!

Answer #2 (Abaye): Even a great person should visit a less important person.

Answer #3 (Rava): One should visit a sick person even 100 times in a day.

(R. Acha bar Chanina): One who visits a sick person alleviates a 60th of his pain (some texts - sickness).

Question (Abaye): If so, 60 people should visit a Choleh, and this will cure him!

Answer #1 (Rava): The sixtieth is like Rebbi's law of a 10th:

(Beraisa - Rebbi): A orphaned daughter who is fed by her brothers receives a 10th of the estate when she gets married. After the first daughter marries, each subsequent daughter receives a 10th of what remains.

(Here, each visitor removes a 60th of the remaining sickness.)

Answer #2 (Rava): Also, only a Ben Gilo removes a 60th of the sickness.

40a: Rava fell sick. The first day, he asked not to publicize the matter, lest his Mazel turn bad. After this, he asked them to announce it.

He reasoned: whoever hates me will rejoice, and it says "do not rejoice in the fall of your enemy (lest Hash-m... will turn His anger away from him)". Whoever loves me will request mercy for me.

41a (Shmuel): The only sick person one should visit is one with a fever.

Question: What does he come to exclude?

Answer (Beraisa - R. Yosi ben Parta): We do not visit those with intestinal sickness, eye problems, or headaches.

Question: Granted, one with intestinal sickness is embarrassed to have visitors. But why don't we visit those with eye problems and headaches?

Answer: Rav Yehudah taught that speaking hurts the eyes and head.

Bava Metzi'a 30b (Rav Yosef): "V'Hodata Lahem" refers to (teaching) a trade (some explain - Torah); "ha'Derech" refers to Chesed; "Asher Yelchu Bah" refers to Bikur Cholim.

Question: Bikur Cholim is included in Chesed!

Answer: The verse obligates visiting Ben Gilo, even though one part in 60 of the sickness goes from the Choleh to the visitor.

Sotah 14a - Question: How can one fulfill "You will go after Hash-m" - "Hash-m is a consuming fire"!

Answer (R. Chama b'Rebbi Chanina): You go in Hash-m's ways;

Hash-m visits the sick - "Hash-m appeared to him in Alonei Mamre" - you should also!

Sanhedrin 19a (Beraisa): When people console a Kohen Gadol (in mourning), the Segan is on his right, the Av Beis Din and everyone else is on his left.

Inference: The Meshuach She'avar (one who once substituted for the Kohen Gadol) does not come to console him.

This is lest the Kohen Gadol think 'he is happy about my loss.'

Rishonim

The Rif brings R. Acha's teaching, Abaye's question, and Rava's answers. He brings why Rava asked to publicize his illness only after the first day.

Ran (39b DH uv'Ben): Ben Gilo is one born with the same Mazel.

Rambam (Hilchos Evel 14:4): The Mitzvah of Bikur Cholim applies to everyone. Even a great person should visit a smaller person, even many times in a day. The more he visits, the better, as long as he does not bother the Choleh. If one visits, it is as if he took part of the illness and alleviated it. If one does not visit, it is as if he murders.

Shevet Yehudah (YD 335:2 DH v'Afilu, brought in Mekoros u'Tziyunim in Frankel Rambam): The Rambam learns from Vayikra Rabah (34:1) that even one who is not Ben Gilo removes a 60th of the illness.

Note: The Medrash says that only one who loves the Choleh like himself removes a 60th. It does not mention Ben Gilo. Etz Yosef says that 'loves him like himself' means that he is Ben Gilo. The Rambam does not mention either love or Ben Gilo! Maharzu says that if he loves him like the love of David and Yonason, he removes a 60th of the illness. If not, he alleviates somewhat.

Einayim l'Mishpat (39b:3): The Rambam brings only what can be understood rationally. He understands 'Ben Gilo' to mean someone of a similar age. This is like Rashi, who says 'a Bochur visiting a Bochur, or an elder visiting an elder.' The Me'iri (DH Mitzvas) says that since one enjoys the visit of Ben Gilo, it lightens the sickness.

Shitah Mekubetzes (39b DH Afilu): Even though a Chacham is exempt from Hashavas Aveidah when it is not dignified for him, this does not exempt from Bikur Cholim. We find that Hash-m visited Avraham on the third day from his Milah; we are commanded to follow His ways.

Poskim

Shulchan Aruch (YD 335:2): Even a great person should visit a smaller person. One should visit many times in a day. The more he visits, the better, as long as he does not bother the Choleh. If one visits a sick person, it is as if he alleviates part of his sickness. If one does not visit, it is as if he murders.

Gra (4): We learn that one should not visit too much if it bothers the Choleh from the Sugya (41a, we don't visit those with eye problems or headaches because speaking hurts the eyes and head).

Rema: Some say that a Sonei (one who hates the Choleh) can visit him. I say that a Sonei should not visit a Choleh or console a mourner, lest it seem that he rejoices over his misfortune.

Darchei Moshe (1): Sanhedrin 19a proves that a Sonei should not console a mourner. Likewise, he should not visit a Choleh.

Maharil (Teshuvah 197): Bikur Cholim is included in Gemilas Chesed and keeping someone alive. We are not commanded to do these for a Rasha who is not considered "Amecha". If Reuven hates Shimon for no proper reason, it is a Mitzvah to visit him more than others. One helps his Sonei to load before helping his friend to unload, in order to overcome his Yetzer Ra, even though causing pain to animals is mid'Oraisa, Tosfos applies this to a lone witness who saw Shimon transgress Ervah, even though he may hate him. If Reuven rejoices over Shimon's misfortune, this helps Shimon, like Rava taught. We are not concerned lest people suspect Reuven of this, just like a Sonei helps to unload, without concern lest people suspect that he rejoices at his enemy's plight. Here also, Reuven helps him; he removes a 60th of the illness.

Note: The Maharil connotes that any visitor removes a 60th of the illness. Perhaps he assumes that we do not know whether or not he is Ben Gilo, so perhaps the visitor removes a 60th of the illness. Alternatively, he holds that 'Ben Gilo' means of a similar age; normally, Son'im are of similar ages.

Maharil (ibid.): A Mudar Hana'ah usually hates the other person. Still, the Gemara says that he visits him, for he did not intend to forbid life essentials through the vow. Rav Yehudah excommunicated a Talmid of ill repute. When Rav Yehudah fell sick, the Talmid came to visit him (Mo'ed Katan 17a).

Rebuttal (Darchei Moshe 1): Perhaps the Talmid accepted the Niduy with love, and did not hate Rav Yehudah. And even if he hated him, perhaps he should not have visited him! Therefore, it is better to refrain (from visiting).

Bach (Sof ha'Siman DH Kasuv): Sefer Chasidim (537) says that one should attend the Levayah of his Sonei, unless the Mes had requested that he not come. It seems that here we are not concerned lest he rejoice at his downfall, for death is the end of man, but a Sonei should not console or visit a Choleh. However, it depends on the hatred and the people involved.