I highlighted major statements by Lenin in two previous posts, but I neglected to add this key programmatic essay:
Lenin, V. I. "Socialism and Religion," in Collected Works, Volume 10 (Moscow: Progress Publishers, 1965), pp. 83-87. Originally published in Novaya Zhizn, No. 28, December 3, 1905.
For additional articles by Lenin on religion, church, and god-building, check this list of titles: