Sirach 12:9-11

New Revised Standard Version Catholic Edition

⁹ One’s enemies are friendly^[a] when one prospers,
    but in adversity even one’s friend disappears.
¹⁰ Never trust your enemy,
    for like corrosion in copper, so is his wickedness.
¹¹ Even if he humbles himself and walks bowed down,
    take care to be on your guard against him.
Be to him like one who polishes a mirror,
    to be sure it does not become completely tarnished.