Iʿlām al-muwaqqiʿīn ʿan rabb al-ʿālamīn (311)
Shaykh Al Islam Ibn Qayyim (RA) said: "A large heart can contain great knowledge just as a large valley can hold a large amount of water; and a small heart can contain knowledge only in proportion to its capacity, just as a small valley holds a small amount of water. The valleys flow according to their size, and hearts receive guidance and knowledge according to their capacity. Just as when the floodwater mixes with the earth and passes over it, it carries with it chaff and foam, so too does guidance and knowledge, when mixed with the hearts, stir up the desires and doubts therein to uproot and remove them. This is like medicine which, when drunk, stirs up the humors (akhlaṭ) of the body, causing the drinker to feel discomfort for a while."