| Quote #1
Thou confort of us wrecches, do me endite
Cecilia's death is the most important thing about her life, because through it, she gains sainthood. In dying but winning eternal life, Cecilia gains victory over the devil by depriving him of her soul. This aligns her with Christ, who also won a victory over the devil, by dying but rising from the dead, winning for himself all Christian souls in the process.
| Quote #2
And if that he may feelen, out of drede
The symbolic weight of this passage is to connect the pleasures of the body (sex) with death. The converse, of course, is that pure, holy love will be rewarded with eternal life.
| Quote #3
And whil we seken thilke divinitee,
Tiburtius's argument here is that the brothers will lose their lives on earth just for seeking the divine secrets of heaven, represented here by Pope Urban. The idea that inquiring into things that are "privy," or secret, might lead one to ruin is not a new one; some people viewed it as overly prideful to inquire too much into "goddes pryvetee."