A Promise (n.) can kill by being kept: Neptune honored his word to Theseus, and Theseus lost his son.
A Promise (n.) lapses when keeping it does harm — to the one it was made to, or to you more than it benefits him.
A Promise (n.) not to use a remedy again must yield when the sick man's dropsy returns: regard should be paid to life and health.
A Promise (n.) is best broken when it was foolish to make: having promised to dance in the forum for a legacy, the least immoral falsehood is to break it and decline the million.
A Promise (n.) can destroy the one it was made to: Phoebus promised Phaethon whatever he wished, and the son, taken up into the father's chariot, was consumed by a thunderbolt.