In the novel Animal Farm, how and why was the commandment "No animal shall wear clothes" changed?

In fact, this commandment was
not specifically changed. The others which were changed to suit the needs of the
pigs, were:

'No animal shall sleep in a bed', which was adjusted to, 'No
animal shall sleep in a bed with sheets,' after the pigs had moved
into the farmhouse and slept in beds, and 'No animal shall kill any other animal,' was altered
to 'No animal shall kill any other animal without cause.' This
change was made after a large number of animals had been executed by 's dogs for confessing that
they were traitors and spies.

Another commandment which was changed is, 'No
animal shall drink alcohol,' to 'No animal shall drink alcohol to
excess,' once the pigs had taken to drinking copious quantities of beer and
whisky. The pigs also adapted the maxim, 'Four legs good, two legs bad,' to 'Four legs good,
two legs better,' when they took to walking on their hind legs and
carrying whips in their trotters.

It was not long after this specific
adjustment had been made that the pigs erased all the commandments and replaced them with a
single nonsensical one on the wall of the big barn, which read:

'All animals
are equal, but some animals are more equal than others.'

Once this senseless
and illogical statement had been put up, it was not strange for the animals to see the pigs
adopting human behaviour and characteristics. The pigs bought a wireless, installed a telephone
and took out subscriptions to magazines and newspapers.

It was
only at this point that the pigs started wearing clothes:

Napoleon himself appearing in a black coat, ratcatcher
breeches, and leather leggings, while his favourite sow appeared in the watered silk dress which
Mrs. Jones had been used to wearing on Sundays.

it is clear that things on the farm had, ironically, gone full circle. The only
difference now was that the other animals were now ruled and enslaved by their own kind and
their masters had, indeed, become almost human themselves, as it is so aptly put in the last
sentence of the novel:

The creatures outside
looked from pig to man, and from man to pig, and from pig to man again; but already it was
impossible to say which was which.