From Wikipedia:
"A Letter to a Hindu" (also known as "A Letter to a Hindoo") was a
letter written by Leo Tolstoy to Tarak Nath Das on 14 December 1908...
The letter caused the young Mohandas Karamchand Gandhi to write to
the world-famous Tolstoy to ask for advice and for permission to
reprint the Letter in Gandhi's own South African newspaper, Indian
Opinion
Russian Wiki elaborates further
Материалы переписки Толстого и Ганди позволили исследователям установить, что все эти
афоризмы на самом деле принадлежали кришнаитскому гуру Премананде
Бхарати (1857—1914) и были взяты из его книги «Шри Кришна: Господь
Любви» (1904)
Translation:
The correspondence between Tolstoy and Gandhi allowed researchers to
establish that all these aphorisms actually belonged to the Krishna
guru Premananda Bharati (1857-1914) and were taken from his book "Sree
Krishna. The Lord of Love" (1904)
The source cited is vol. 80 of The Complete Works of Tolstoy, Moscow, 1955. This volume is put online. The edition mentioned is Baba Premanand Bharati, «Shree Krishna. The Lord of Love», New York, 1904.
Recent edition is available on Amazon.