Here’s a good thread on this.

Reply to an Inquiry of the Jewish News Agency in the United States

Source: Works, Vol. 13, 1930 - January 1934 Publisher: Foreign Languages Publishing House, Moscow, 1954

"National and racial chauvinism is a vestige of the misanthropic customs characteristic of the period of cannibalism. Anti-semitism, as an extreme form of racial chauvinism, is the most dangerous vestige of cannibalism.

Anti-semitism is of advantage to the exploiters as a lightning conductor that deflects the blows aimed by the working people at capitalism. Anti-semitism is dangerous for the working people as being a false path that leads them off the right road and lands them in the jungle.

Hence Communists, as consistent internationalists, cannot but be irreconcilable, sworn enemies of anti-semitism. In the U.S.S.R. anti-semitism is punishable with the utmost severity of the law as a phenomenon deeply hostile to the Soviet system. Under U.S.S.R. law active anti-semites are liable to the death penalty."

• J. Stalin January 12, 1931

www.marxists.org/reference/archive/stalin/works/1931/01/12.htm