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.
(R.S. § 41.)