If you sell a book to someone, that is better than your speaking to them - what will your three minutes' preaching do? But if they read a book it may turn their life. Go on preaching, that is the highest perfection of activity, and do not worry for anything, Krishna is so much appreciative of this preaching work that He will give you every facility, as much as you have ambition.
Letter to Brahmananda, 3 November, 1972