Good News Translation
Watch out, and be on guard against him, even if he acts ever so humble. He is like a metal mirror that rusts away if you don't keep it polished.

New Revised Standard Version
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.

Contemporary English Version
eating away at an unpolished mirror. So be on guard against them, even if they bow down and act humble.

New American Bible
Even though they act deferentially and peaceably toward you, take care to be on your guard against them. Treat them as those who reveal secrets, and be certain that in the end there will still be envy.

Douay-Rheims Bible
Though he humble himself and go crouching, yet take good heed and beware of him.

Though he humble himself and go crouching, yet take good heed and beware of him.

Sirach 12:9
In the prosperity of a man, his enemies are grieved: and a friend is known in his adversity.

Sirach 12:10
Never trust thy enemy for as a brass pot his wickedness rusteth:

Sirach 12:12
Set him not by thee, neither let him sit on thy right hand, lest he turn into thy place, and seek to take thy seat and at the last thou acknowledge my words, and be pricked with my sayings.

Sirach 12:13
Who will pity an enchanter struck by a serpent, or any that come near wild beasts? so is it with him that keepeth company with a wicked man, and is involved in his sins.