Peter sees the replacement of Judas as a fulfillment of what is prophesied in Psalm 109:8. Psalm 109 is a prayer of the believer that the days of wicked men might be cut short and their leadership position in communities given to someone else.1 Judas has shown himself to be a wicked man (opposed to God and his King).
20 “For it is written in the Book of Psalms, “‘May his camp become desolate, and let there be no one to dwell in it’;and “‘Let another take his office.’