Charles H. Spurgeon on Psalms 109:8

Let his days be few. By "his days", he meant the days of his apostleship, which were few; since before the passion of our Lord, they were ended by his crime and death. And as if it were asked, What then shall become of that most sacred number twelve, within which our Lord willed, not without a meaning, to limit his twelve first apostles? he at once addeth, and let another take his office. As much as to say, let both himself be punished according to his desert, and let his number be filled up. And if any one desire to know how this was done, let him read the Acts of the Apostles. —Augustine.