Per 《
新华成语词典》, derived from the 《
慈恩传》 (Tang biography of Xuanzang):
唯谈玄论道，
问因果报应 — 'they spoke only of metaphysics and asked about karmic retribution.' A Buddhist import:
因 (cause) +
果 (effect, fruit) = the seed-and-fruit metaphor underlying karma. The doctrine bridges this life and the next, motivating both moral conduct and the genre of Chinese morality tales (
劝善书).
