Talmud do Ozeasza 4:16

(Rabbi Nehorai would say: Exile yourself to a place of Torah [and do not say that it will come to you, or that your colleagues will do it for you. And do not rely on your own understanding.]) He would also say: Do not disparage any person ([and do not dismiss anything]), as it says (Proverbs 13:13), “One who disparages a principle will become injured through it; one who respects a command will be rewarded.”
He would also say: One who studies Torah in his youth, what is he like? Like a calf which was tamed when it was still small, as it says (Hosea 10:11), “Ephraim became a trained calf, but still wanted to thresh.” One who studies Torah in his old age is like a cow that was never trained until it was too old, as it says (Hosea 4:16), “Israel turned away like a stubborn cow.”
He would also say: One who studies Torah in his youth is like a woman who kneads dough when it is hot. One who studies Torah in his old age, what is he like? Like a woman who kneads dough when it is cold.