“Which reminded me… I still owed the gods a debt.
"You're a genius," I (Percy) told Annabeth.”

Source: The Last Olympian

Source: The Lightning Thief

Source: The Mark of Athena

Macheath, Act III, sc. xi, air 57
The Beggar's Opera (1728)

Speech to students at Cambridge University (4 December 1857)
Context: People talk of the sacrifice I have made in spending so much of my life in Africa. Can that be called a sacrifice which is simply paid back as a small part of a great debt owing to our God, which we can never repay? Is that a sacrifice which brings its own blest reward in healthful activity, the consciousness of doing good, peace of mind, and a bright hope of a glorious destiny hereafter? Away with the word in such a view and with such a thought! It is emphatically no sacrifice. Say rather it is a privilege. Anxiety, sickness, suffering, or danger now and then with a foregoing of the common conveniences and charities of this life, may make us pause and cause the spirit to waver and the soul to sink; but let this only be for a moment. All these are nothing when compared with the glory which shall be revealed in and for us. I never made a sacrifice.

Source: The Last Temptation of Christ (1951), Ch. 10