法苑珠林 88.123

88.123

又智度論。問曰。白衣居家唯有此五戒。更有餘法耶。答曰。有一日戒六齋日持。功德無量。若十二月至十五日。受持此戒。福最多也。

Furthermore, the Mahāprajñāpāramitā-śāstra asks: "Do laypeople living at home only have these five precepts, or are there other dharmas?" Answer: "There is the one-day precept maintained on the six fasting days, which possesses immeasurable merit. If one receives and maintains this precept from the twelfth to the fifteenth day, the blessings are the greatest."