2 U.S. Code § 4522
2 U.S. Code § 4522 is about Deductions for withdrawal. It is under Part B (Administration) of Subchapter I (General) of Chapter 45 (Congressional Pay and Benefits) of Title 2 (The Congress) of the Code.
When any Member or Delegate withdraws from his seat and does not return before the adjournment of Congress, he shall, in addition to the sum deducted for each day, forfeit a sum equal to the amount which would have been allowed by law for his mileage in returning home; and such sum shall be deducted from his compensation, unless the withdrawal is with the leave of the Senate or House of Representatives respectively.