This passage supposedly originated from a “Letter to an Anti-Zionist Friend” in an August 1967 edition of Saturday Review. But researchers have found no letters from Dr King in any of the four August 1967 editions. Some have claimed that the letter was also published in a book by Dr King entitled, This I Believe: Selections from the Writings of Dr. Martin Luther King Jr. But according to Electronic Intifada, “no such book was listed in the bibliography provided by the King Center in Atlanta, nor in the catalogs of several large public and university libraries.” A recent search of all electronic databases confirms this.

https://www.jacobinmag.com/2019/02/martin-luther-king-israel-palestine-occupation