Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: "Hold fast to acquiring knowledge before it is taken away, and its being taken away is the passing of the people of knowledge. Hold fast to knowledge, for none of you knows when people will come to need the knowledge he has. Hold fast to knowledge, and beware of affectation and delving too deep, and hold fast to the old way, for soon there will come people who recite the Book of Allah but cast it behind their backs."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8813