It is narrated from the Prophet of Islam (PBUH) who said:

Do Jihad against your inordinate desires of soul, as you do Jihad against your enemies [1]. In another narration, the first Shia Imam, Ali ibn Abitaleb (AS) said: And how much of wisdoms are captives of the dominating inordinate desires which rule over them [2]. Therefore, without Jihad against inordinate desires, it is not possible to liberate wisdom from captivity. Rather it is necessary to capture inordinate desires and liberate wisdom in order to be able to reason and comprehend in thought and motivation, and to secure great goals and attain accomplishment.

[1] Al-Mofradat fi Qarib Al-Quran, Raqib Isfahani, Page 101.

[2] Sharh Nahjul Balaghah, Ibn Abil Hadeed, Vol. 19, Page 31.

Source:en.shafaqna.com