The early sages (the Tanaaim) ruled that a person who carries another living person on a bed on the Sabbath is not violating the law against taking items from domain to domain on the Sabbath, but one who carries a dead man on a bed is transgressing the prohibition on carrying from domain to domain on the Sabbath.
The scholars supposed that the distinction between carrying a dead man and a live one is not universally accepted and is the opinion only of Rabbi Nathan, who said “One who carries a animal or bird into the public domain — if it has been slaughtered he is liable and if it is alive he is exempt, for the live carry themselves.” One of the scholars, Rava, thought that carrying a live person is not considered a transgression by any sage at all. But some of the sages draw a distinction between carrying a live animal or bird and carrying a live person. The reason for the distinction between them is that animals tend to resist being carried and make it difficult for the one carrying them, so one who carries them from domain to domain on the Sabbath violates the prohibition against carrying things from domain to domain. But a live person does not tend to resist, so the person who carries him from domain to domain does not violate the prohibition against carrying things from domain to domain on the Sabbath. The scholars asked: If one who lifts and carries a person is not considered to be doing prohibited work, why did one of the sages rule that if a living person rides a horse on the Sabbath, the horse’s owner is not liable for transgressing the prohibition on letting one’s animals work except in the opinion of a minority of the sages? Answer: When they allowed this use of a horse, they meant a horse which carries birds and not people. The scholars asked: Is there such a thing as a horse which carries only birds? Answer: Yes! There is a horse which is used only by bird hunters upon which they carry their trained birds of prey (falcon, hawk). The scholars added that if the living man is tied and bound, one who carries him transgresses the prohibition against carrying things from domain to domain on the Sabbath. The scholars asked why gentile Persians were allowed to ride horses belonging to Jews; the Persians are considered as being tied and bound because of the vast amounts of garments they wear and because they do not dismount. Answer: The Persians wear such clothes and are not accustomed to walking not because they are bound, but because of excessive pride which does not permit them to exert themselves in front of their own people. Proof of the matter is that one Persian sprinted 12 kilometers because he feared the king, who was angry at him.
(Babylonian Talmud, Tractate Shabbat 94a)