The Seven Commandments are the basic principles of animalism worked out by the pigs and described originally as "unalterable laws" by which the animals were to live. The Seven Commandments were written on the barn wall for all animals to see and read if they could. The original Commandments are:
1. whatever goes on two legs is an enemy.
2. Whatever goes on four legs, or has wings, is a friend.
3. No animal shall wear clothes.
4. No animal shall sleep in a bed.
5. No animal shall drink alcohol.
6. No animal shall kill any other animal.
7. All animals are equal.
Almost immediately after the Commandments are written the cows have to be milked. The milk they produce is taken by the pigs exclusively so the seventh Commandment seems to be undermined from the very beginning. When the pigs also start claiming the windfall apples, Squealer explains that they are not taking them as privilege but because science has shown that milk and apples are necessary for the pigs' "brain work". This at least satisfies the animals that they are equal to the pigs but it does not fool the reader.
The first two Commandments are subtly broken in the first years of Animal Farm but there is no attempt to rewrite them. Snowball, the hero of the Battle of the Cowshed, becomes an enemy of the farm after his expulsion by Napoleon, while the resumption of trade via Mr Whymper causes some discussion but, as Squealer points out, trade was not banned in writing and Mr Whymper is not treated as a friend.
The first alteration to the Commandments comes after the pigs move back into the farmhouse. The ban on sleeping in beds is changed in Napoleon's favor by the addition of the words "with sheets". At this point in the history of the farm the pigs do not quite have enough power to do what they like and Squealer is forced to change the Commandments to fit new circumstances. But sleeping in beds is a minor matter compared...