Mishkat al-Masabih #208

Anas reported God’s messenger as saying, “The search for knowledge is an obligation laid on every Muslim, but he who commits it to those who are unworthy of it is like one who puts necklaces of jewels, pearls and gold on swine.” Ibn Majah transmitted it. Baihaqi transmitted it in Shu'ab al-iman up to the word “Muslim”, saying that this is a tradition whose text is well known but whose isnad is weak, it being transmitted by many ways all of which are weak.