In a letter to his officials, Imam Ali (AS) wrote:

Whoever does not take his responsibility seriously, and betrays it, and does not cleanse his body and religion from deception, has opened the doors of indignity to himself in this world, and the severity of his indignity will be harsher in the hereafter. Certainly, betrayal of nation is the biggest treachery, and the deception by leaders is the ugliest of deceptions [1].

[1] Nahjul Balaghah, Letter 26.

Source: en.shafaqna.com