"Much may be done by means of a little knowledge, and knowledge should not be separated from action," says the 11th Century Sufi, Ali Hajweri (Data Ganj Bakhsh) in the first chapter of his seminal work Revelation of the Mystery (Kashful Mahjub). Here is the opening passage.
God has said, describing the savants [ulema], “Of those who serve God only the savants fear Him” (Quran, Chapter 35, Verse 25). The Prophet said, “To seek knowledge is obligatory on every Muslim man and woman”; and he said also, “Seek knowledge even in China.”
Knowledge is immense and life is short: therefore it is not obligatory to learn all the sciences, such as Astronomy and Medicine, and Arithmetic, etc., but only so much of each as bears upon the religious law: enough astronomy to know the times [of prayers] in the night, enough medicine to abstain from what is injurious, enough arithmetic to understand the division of inheritances and to calculate the duration of the idda [the period within which a woman, who has been divorced or whose husband has died, may not marry again], etc.
Knowledge is obligatory only in so far as is requisite for acting rightly. God condemns those who learn useless knowledge (Quran, Chapter 2, Verse 96), and the Prophet said, “I take refuge with You from knowledge that profits nothing.”
Much may be done by means of a little knowledge, and knowledge should not be separated from action. The Prophet said, “The devotee without divinity is like a donkey turning a mill,” because the donkey goes round and round over its own tracks and never makes any advance.
Some regard knowledge as superior to action, while others put action first, but both parties are wrong. Unless action is combined with knowledge, it is not deserving of recompense. Prayer, for instance, is not really prayer, unless performed with knowledge of the principles of purification and those which concern the qibla [the point to which a Muslim turns his face while worshipping, viz. the Kaaba], and with knowledge of the nature of intention. Similarly, knowledge without action is not knowledge. Learning and committing to memory are acts for which a man is rewarded in the next world; if he gained knowledge without action and acquisition of his part, he would get no reward.
Hence two classes of men fall into error: firstly, those who claim knowledge for the sake of public reputation but are unable to practice it, and in reality have not attained it; and secondly, those who pretend that practice suffices and that knowledge is unnecessary. It is told of Ibrahim b. Adham that he saw a stone on which was written, “Turn me over and read!” He obeyed, and found this inscription: “You do not practice what you know; why, then, do you seek what you know not?” Anas b. Malik says, “The wise aspire to know, the foolish to relate.” He who uses his knowledge as a means of winning power and honor and wealth is no savant.
The highest pinnacle of knowledge is expressed in the fact that without it none can know God.