“Wisdom is the believer's lost treasure; he takes it wherever he finds it.”

This is worth being precise about. The sentence circulates as a saying of the Prophet (peace be upon him), and it does appear in the Sunan of al-Tirmidhi and Ibn Majah — but al-Tirmidhi himself called the report unusual, and hadith critics grade the chain very weak because of a narrator the specialists agreed was unreliable. It is kept here as wisdom literature rather than as an established hadith.