When Sergeant Morris visits with the White family, you will notice that he is very reluctant to share information about the monkey's paw. It is Mr. White who engages him in conversation about it. Morris tries to dismiss it as a bit of "magic," but this only serves to pique the White's curiosity.
Reluctantly, Sergeant Morris tells them that the paw had a spell put on it by an old "fakir" (religious man) who wanted to use it to teach people about the power of fate. Specifically, he wanted to show people that interfering with fate has serious consequences. In order to demonstrate this, explains Morris, the fakir created a spell which gave three wishes to three separate men.
Morris continues to say that he is the second man to own the monkey's paw. The first man had his three wishes, the third being death, and so the paw came into Morris's possession. Having already had his three wishes, Morris thought about selling the paw, but it has caused so much "mischief" that he thinks a buyer seems unlikely.
It is interesting to note that Morris does not reveal his wishes to the White family. Instead, he leaves the paw in their possession and tells them to wish for something "sensible"—if they must wish for anything at all.