كن بعدوك العاقل أوثق منك بصديقك الجاهل
Have more trust in a rational enemy than in a stupid friend.
A sane person doesn’t trust his enemies and is cautious when dealing with them. The Imam says that we have to be even more cautious with our friends if they are stupid. This is because a stupid friend may reveal your secrets, embarrass you, or get you into trouble.
أعدى عدو للمرء غضبه وشهوته فمن ملكهما علت درجته وبلغ غايته
The fiercest enemies of any human are his own anger and craving, and whoever controls them will ascend and reach his purpose.
Craving is the literal translation from the Arabic word: الشهوة . In this quote it includes the variety of human desires: appetite for food, sexual desire, seeking power and fame, etc…
A distinction must be drawn here between seeking and satisfying the necessary desires of a human being (which the Islamic jurisprudence allows us to do), and the overwhelming addiction to lust, power, food, etc…, which is not normal. The latter is what the Imam refers to as your enemy, not the former.
Anger is also considered to be an enemy, and this quote is in line with the modern wave of anger management techniques and efforts.
The Imam is warning us about those two enemies, they are dangerous because they are fierce and invisible. He also shows us our purpose in life: to win the battle against anger and demonic desires, and this winning results in reaching spiritual perfection and ascent into Heaven.