“Truly!
I say to you!
‘All this will come
Upon this generation.’”
ἀμὴν λέγω ὑμῖν, ἥξει ταῦτα πάντα ἐπὶ τὴν γενεὰν ταύτην.
This is a saying unique to Matthew. Jesus said to these Pharisees and Scribes with a solemn pronouncement (ἀμὴν λέγω ὑμῖν) that all these things would happen to this generation (ἥξει ταῦτα πάντα ἐπὶ τὴν γενεὰν ταύτην), right away, before any of them died.