Musannaf Ibn Abi Shayba 33:88

Ibn Numayr narrated to us, he said: Mu'awiyah al-Nasri narrated to us, from Nahshal, from al-Dahhak ibn Muzahim, from al-Aswad, who said: Abdullah said: "If the people of knowledge had guarded their knowledge and placed it only with those worthy of it, they would have become masters over the people of their time through it. But they offered it to the people of the world so that they might attain some of their worldly gains through it, so they became insignificant to them." I heard your Prophet say: "Whoever makes his concerns a single concern, Allah will suffice him for the concerns of his Hereafter. And whoever has his concerns scattered among the affairs of the world, Allah will not care in which of its valleys he perishes."