Hawzah News Agency – The commander of the faithful, Imam Ali peace be upon him says:

أعدى‏ عَدوِّكَ نَفسُكَ الَّتي بَينَ جَنبَيكَ.

‘Your archenemy is your lower self that resides between your two sides.’

Source: Tanbih al-Khawatir, v. 1, no. 259