Sa'id bin Wahb (may Allah have mercy on him) narrates that Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: "People will continue to hold firm (to the religion) as long as knowledge reaches them from the Companions of Muhammad (peace and blessings be upon him) and from their elders; but when it begins to reach them from the young ones (people of little knowledge and little standing), at that time they will be destroyed."
Hadith Referenceالمعجم الأوسط / باب الميم / 7590
Hadith Takhrij«أخرجه عبد الرزاق فى «مصنفه» برقم: 20446، 20483، والطبراني فى «الكبير» برقم: 8589، 8590، 8591، 8592»