John Gill Commentary Luke 21:31

"Even so ye also, when ye see these things coming to pass, know ye that the kingdom of God is nigh." — Luke 21:31 (ASV)

So likewise when you see these things come to pass
The signs before mentioned, in (Luke 21:8–11Luke 21:20Luke 21:25Luke 21:26) . Know you that the kingdom of God is nigh at hand :
a more visible and glorious display of the kingdom of the Messiah, in the destruction of his enemies, the Jews; see (Mark 9:1) .