Sufyaan Ath-Thawree (May Allaah have mercy upon him) said:
 

"The first (level) of knowledge is (observing) silence. The second is listening attentively and memorizing it. The third is acting in accordance to it. The fourth is spreading and teaching it."

(Lammad Durral-Manthoor minal-Qawlil-Ma-thoor # 173