Jamieson, Fausset and Brown on Revelation 21:14

14. twelve foundations--Joshua, the type of Jesus, chose twelve men out of the people, to carry twelve stones over the Jordan with them, as Jesus chose twelve apostles to be the twelve foundations of the heavenly city, of which He is Himself the Chief corner-stone. Peter is not the only apostolic rock on whose preaching Christ builds His Church. Christ Himself is the true foundation: the twelve are foundations only in regard to their apostolic testimony concerning Him. Though Paul was an apostle besides the twelve, yet the mystical number is retained, twelve representing the Church, namely thirty the divine number, multiplied by four, the world number.

in them the names, &c.--As architects often have their names inscribed on their great works, so the names of the apostles shall be held in everlasting remembrance. Vulgate reads, "in them." But A, B, Syriac, Coptic, and Andreas read, "upon them." These authorities also insert "twelve" before "names."