It was narrated from Anas bin Malik that the Messenger of Allah (ﷺ) said:
"Seeking knowledge is a duty upon every Muslim, and he who imparts knowledge to those who do not deserve it, is like one who puts a necklace of jewels, pearls and gold around the neck of swines."
English reference: Vol. 1, Book 1, Hadith 224
Arabic reference: Book 1, Hadith 229