Glossa Ordinaria

"It happened," etc. Let no one wonder if sometimes a good thing typically signifies an evil, and evil things a good. For if this were not allowed, the name of God would never be written with black ink, but always with shining gold, because God is light. But if you write the name of the devil with a white stone, it nonetheless signifies darkness. Tobias, therefore, being blinded, signifies the people of Israel. "For blindness in part has happened in Israel." Wearied from burying, he was blinded. For he who persists untiring in good works does not admit the light of faith. Thus he sleeps wearied in a spiritual manner who neglects to watch, to stand, to act manfully, and to be strengthened. To whom it is said: "Rise, thou that sleepest, and arise from the dead." Swallows, because of their light flight, signify pride and levity; and their uncleanness blinds those over whom it holds sway. He sleeps placed beneath a swallow's nest who unwarily subjects himself to the levity of wantonness and to pride. This blindness prevailed most of all over the people of Israel when the Lord's coming in the flesh was at hand, when it laboured under the yoke of Roman servitude and violated the precepts of the divine law by living badly.