feather one's own nest
To look after one's own interests, especially material ones: “The director was supposed to distribute the money to various charities; instead, he used it to feather his own nest.”
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.