A.T. Robertson Commentary Matthew 19:28

"And Jesus said unto them, Verily I say unto you, that ye who have followed me, in the regeneration when the Son of man shall sit on the throne of his glory, ye also shall sit upon twelve thrones, judging the twelve tribes of Israel." — Matthew 19:28 (ASV)

In the regeneration (εν τη παλινγενεσια). The new birth of the world is to be fulfilled when Jesus sits on his throne of glory. This word was used by the Stoics and the Pythagoreans. It is common also in the mystery religions (Angus, Mystery Religions and Christianity, pp. 95ff.). It is in the papyri also. We must put no fantastic ideas into the mouth of Jesus. But he did look for the final consummation of his kingdom. What is meant by the disciples also sitting on twelve thrones is not clear.