Augustine of Hippo

(ubi sup.) Or it is an expression to denote that there is nothing that shall go unpunished; as we say ‘To the dregs,’ when we are speaking of any thing so emptied that nothing is left in it. Or by the last farthing (quadrans.) may be denoted earthly sins. For the fourth and last element of this world is earth. Paid, that is in eternal punishment; and until used in the same sense as in that, Sit thou on my right hand until I make thy enemies thy footstool; (Ps. 110:1.) for He does not cease to reign when His enemies are put under His feet. So here, until thou hast paid, is as much as to say, thou shalt never come out thence, for that he is always paying the very last farthing while he is enduring the everlasting punishment of earthly sins.