Maintaining the number of Disciples Acts 1:24-26;  And they prayed and said, “You, Lord, who know the hearts of all men, show which one of these two You have chosen, to occupy this ministry and apostleship from which Judas turned aside to go to his own place.” And they drew lots for them, and the lot fell to Matthias; and he was added to the eleven apostles.


Why did they want to have 12 disciples? There is a question about it but I wish to know the importance of having 12 Disciples.  Why could not there be only 11 Disciples.  I have tried a few websites but none gave any information about this.
The early Church Fathers taught that the twelve Apostles corresponded to the twelve tribes of Israel, even though each Apostle was not from a different tribe.  For example:


  To these He gave authority to preach the Gospel, being twelve in
  number, corresponding [lit. in witness to] to the twelve tribes of
  Israel.
  
  The Epistle of Barnabas (late 1st/early 2nd cent.)