A Pauper's oath is a sworn statement or oath by a person that he or she is completely destitute or a pauper, i.e. without any money or property.
A person without the ability to pay court costs has the option to swear a pauper's oath in order to file a lawsuit without paying filing fees. Prisoners filing legal actions often use a pauper's oath because persons in prison are often completely without money or any means of acquiring any.
Historically, especially during the Great Depression, the pauper's oath was required as a prerequisite for receiving welfare or other forms of government relief in the United States.
One pauper's oath used when establishing indigent status under United States Federal law is as follows:
References
Pauper's oath Wikipedia(Text) CC BY-SA