Beatty compares Montag to Icarus. Icarus was the son of Daedulus, a great craftsman who made Icarus wings that would allow him to fly. Daedulus warned him not to go too near to the sun, but Icarus went ahead and did so anyway, melting the wax on his wings so that he plunged into the sea and drowned.
"Well," said Beatty, "now you did it. Old Montag wanted to fly near the sun and now that he's burnt his damn wings, he wonders why. Didn't I hint enough when I sent the Hound around your place?"
The firemen have just responded to a call, and Beatty has withheld the information that it is Montag's home they are burning until they pull up the house. Mildred has turned Montag in for having books.
The statement is significant for several reasons. First, it shows overtly what was implicit all along: Beatty sees himself as a father figure to Montag. He warned Montag to stay from books, and Montag did not listen. He will have to pay the price, with Beatty as the punishing father figure. Further, the statement once again shows how well-read Beatty is, a man completely steeped in good literature. This sign of intelligence, combined with his increasingly cruel verbal bullying of Montag, suggests that Beatty, like Mildred, is suicidally frustrated with the society in which he lives. On one hand, he is its voice of orthodoxy and has grown to a position of prestige and power through repressing reading, but on the other hand, his words hint that he is eaten with secret envy at the path Montag has taken. After all, Icarus is a figure that culturally has been admired (along with being condemned) for his audacity in reaching for the stars, and he is often used as the metaphor for the artist, doomed to failure but determined anyway to soar.
The words are also ironic: Beatty believes he has won and that Montag is finished, but, in fact, it is the other way around.