Book 15: 《衛靈公》 Wei Ling Gong (Duke Ling of Wey)
《衛靈公》 Passage 15.31
子曰：「吾嘗終日不食，終夜不寢，以思，無益，不如學也。」
Legge Translation (1861)
The Master said: "I have been the whole day without eating, and the whole night without sleeping: — occupied with thinking. It was of no use. The better plan is to learn."