The "Sefer Chafetz Chaim" (or Chofetz Chaim or Hafetz Hayim) (Hebrew: חָפֵץ חַיִּים, trans. Desirer of Life) is a holy book (hebr.: sefer) on the Jewish ethics and laws of speech written by Rabbi Yisrael Meir Kagan, who later became know simply as The Chofetz Chaim.
The book 
The title of the work Chafetz Chaim by Rabbi Yisrael Meir Kagan is taken from Psalms :
Come, children, hearken to me; I will teach you the fear of the Lord. Who is the man who desires life, who loves days to see goodness? Guard your tongue from evil and your lips from speaking deceitfully. Shun evil and do good, seek peace and pursue it.
The subject of the book is Lashon Hara. Rabbi Kagan provides copious sources from the Torah, Talmud and Rishonim (early commentators) about the severity of Jewish law on tale-mongering and gossip. Lashon hara , meaning evil speech (or loosely gossip and slander and prohibitions of defamation), is sometimes translated as prohibitions of slander, but in essence is concerning the prohibitions of saying evil/bad/unpleasant things about a person, that are true.
The book is divided into three parts:
- Mekor chayim ("Source of Life"), the legal text.
- Be'er mayim chayim ("Well of living water"), the footnotes and legal argument.
- It is commonly printed together with the text Shemirath ha-Lashon ("Guarding of the tongue"), an ethical treatise on the proper use of the faculty of speech.
Rabbi Israel Meir HaCohen Kagan is commonly known as the "Chafetz Chaim," the name of his famous work on guarding one's tongue. He was born in Zhetel, Poland on February 6, 1838. As his reputation grew, students from all over Europe flocked to him and by 1869 his house became known as the Radin Yeshiva. The Chafetz Chaim published 21 sefarim (holy books). His first work, Sefer Chafetz Chaim (1873), is the first attempt to organize and clarify the laws regrding Lashon Hara. He later wrote Sefer Shmirat HaLashon, which emphasized the importance of guarding one's tongue by quoting our Sages. The Mishnah Brurah (1894-1907), a commentary on the Daily Jewish Laws, is accepted universally to decide Halacha.
- "Chofetz Chaim Biography". Ethics of Speech. Project Genesis. Retrieved 18 January 2013.