Nahj al-Balāgha

Hadith 1905
governance
٣٤٨. وَقَالَ (عليه ‏السلام): أَشدُّ الذُّنُوبِ مَا اسْتَهَانَ بِهِ صَاحِبُهُ.
348. Amīr al-mu’minīn, peace be upon him, said: The most serious sin is that which the doer considers light. [1]
Source: al-Sharīf al-Raḍī