The first Shia Imam, Ali (AS) said:

Before its tree is dried, try to attain knowledge and learn about sciences, and before you engage in yourselves, extract from the mine of sciences (meaning; the Quran and Ahlul Bayt (AS)). Prohibit the people from Haram and Monkarat (inappropriate acts), and also do not commit them yourselves; because it has been commanded that first you must abandon forbidden acts (Moharramat) yourself and then prohibit others from them [1].

[1] Nahul Balaghah, Sermon 105.

Source:en.shafaqna.com