The Significance Of 166

Megillas Esther contains 166 verses. This is also the precise number of words in the portion of Amalek (Shemos 17:8-16; Devarim 25:17-19). The Great Hallel (Tehillim 136) also contains 166 words; it is a praise for Hashem's saving us from all our enemies.

(Me'am Lo'ez)