With envious tooth who others tear,
May find their bite retorted here.
A Viper in a cutler's shop,
Sought on some eatable to drop;
He bit a File; with haughty tone
Who said, "Vain fool! let me alone;
Thinks thou that he thy tooth will feel,
Who bites himself the hardest steel?"
Source: Boothby - Phaedrus 4.8.