In Animal Farm, Moses is allowed to return to the farm. What does he have to say? How do the animals respond?

Moses is a tame raven who lives on Manor Farm before the animals take over. Mr. Jones treats him like a pet and feeds him bread crusts, but most of the animals hate him because he does no useful work and produces nothing of value. He is known for being a spy and telling tales:

He claimed to know of the existence of a mysterious country called Sugarcandy Mountain, to which all animals went when they died. It was situated somewhere up in the sky, a little distance beyond the clouds, Moses said. In Sugarcandy Mountain it was Sunday seven days a week, clover was in season all the year round, and lump sugar and linseed cake grew on the hedges...

Although most of the animals resent him, some believe his stories about Sugarcandy Mountain. The pigs consider Sugarcandy Mountain to be a myth that is antithetical to the teachings of Animalism, and with some difficulty they manage to convince the other animals of this.

When the animals revolt, Moses flees with Mrs. Jones, and he is not seen again until the end of the novel, when he reappears spreading the same tales of Sugarcandy Mountain. The pigs still claim to loathe him, but they tolerate his presence and even give him a weekly ration. As for the others,

Many of the animals believed him. Their lives now, they reasoned, were hungry and laborious; was it not right and just that a better world should exist somewhere else?

The character of Moses represents religion, specifically the Russian Orthodox Church. The first communists believed that religion was a tool that the ruling class used to keep the lower classes in line, as expressed by Karl Marx in his famous statement that “religion is the opiate of the masses.” Just as the communists thought that the hope of heaven was a dream that kept the poor and downtrodden workers from trying to improve their lot on Earth, so the pigs thought that Moses’ “Sugarcandy Mountain” was a distraction from the work of creating an animal-run utopian farm. 

Once Napoleon has taken over and the pigs give up on an egalitarian utopia in favor of accumulating power and wealth, however, they allow Moses to return and preach a message that will give the animals hope despite their present situation. They keep and feed Moses just as Jones did, because he is useful to them, and because in many ways they have become just like Jones.