Searching for quotation about self-sacrficing teachers

Somewhere in the movies/on television recently, a character recited a quotation from a prominent 19th century (?) figure about teachers sacrificing their lives so that they may help the next generation. As a former teacher, I am interested in getting this quote.

Can anyone provide me quote?

Oldmaid85, I’m not sure if this is it, but I found this quote:

I found it here, which is a site of teaching-related quotations, and the quote above is referred to as “The Essence of Teaching.” However, a quick google search seems to indicate that the author is unknown.