The alterations in the commandments of the animals exemplifies how power corrupts. For, once Napoleon has eliminated Snowball as his only competition and gained power, he has become a dictator with vicious dogs to enforce his rules and Squealer as his propagandist to keep the other animals from voicing objections.
And, since Napoleon now has absolute power, the rules are bent to fit him. In addition, he uses trickery and the "spin" that Squealer puts upon truth in order to enrich himself. He is so convincing that he makes the animals believe that the rules have always the way that they presently are, proving that whoever controls language controls society. In Chapter 6, for instance, Squealer speaks t0 the other animals,
"You did not suppose, surely, that there was ever a ruling against beds? A bed merely means a place to sleep in. A pile of straw in a stall is a bed, properly regarded. The rule was against sheets, which are a human invention. We have removed the sheets from the farmhouse beds, and sleep between blankets...."
For the most part, the wording of the rules has changed, or words to categorize the rules differently have been added. In one instance, there has been a rule that no animal can sleep in a bed. But, because the pigs gradually become like the humans--the oppressors whom they have overthrown--the rule is altered to read "No animal shall sleep in a bed with sheets." The alterations to the rules erode the freedom of the animals to the point that they become worse off than they were with Mr. Jones.