| Quote #1
"It had a spell put on it by an old fakir," said the sergeant-major, "a very holy man. He wanted to show that fate ruled people's lives, and that those who interfered with it did so to their sorrow. He put a spell on it so that three separate men could each have three wishes from it." (1.26)
This implies that the paw is just plain evil, that any wish made on it will have bad consequences. It sounds like a caution against using magic to change the course of our lives. Since most of us don't have access to magic, it could be read as warning against trying to get things the easy way, or against taking unnecessary risks – such as gambling.
| Quote #2
"If you could have another three wishes," said the old man, eyeing him keenly, "would you have them?" […]
The paw seems to bring out greed and desire in those who come in contact with it. To some degree, it seems to have the power to rob people of their free will.
| Quote #3
"I suppose all old soldiers are the same," said Mrs White. "The idea of our listening to such nonsense! How could wishes be granted in these days? And if they could, how could two hundred pounds hurt you, father?" (2.2)
Here's what Mrs. White is basically saying: since the paw can't really grant wishes, there can't be any harm in wishing on it. Later it seems she really does believe in the paw and is trying to convince her husband to use it. This helps us see that beneath her cheerful demeanor, she is a little desperate for anything that might turn their lives around.