line one's pockets
line one's pockets also line one's purse {v. phr.}, {informal}
To get a lot of money unfairly; get rich by being dishonest.
The policeman lined his pockets by taking bribes.
The inspector lined his pockets by permitting contractors to use poor building materials.
Compare: FEATHER ONE'S NEST.
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Source: A Dictionary of American Idioms