It is narrated from Sayyiduna Abu Umamah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Acquire knowledge before it runs out" (he said it three times). The Companions said: O Messenger of Allah! How will it run out when the Book of Allah is among us? He (peace and blessings be upon him) became angry (may Allah never make him angry), then said: "May your mothers be bereft of you! Did the Bani Isra'il not have the Torah and the Injil, yet they were of no use to them at all? Indeed, the departure of knowledge is the departure of its bearers (the people of knowledge)" (he said it three times).
Hadith Referenceالمعجم الكبير للطبراني / باب الصاد / 7875