[...] You are mistaken if you believe that when I address you as "friend"—a title which you do not think you can return—I am using the word in a conventional sense. You may still be in doubt whether I am your friend; this depends on your feelings! I for my part cannot explain your behaviour, your decision in my favour, as proceeding from merely business considerations, but rather as called forth by genuinely friendly sentiments. Accordingly, it is on good and well-considered grounds that I call you my friend. [...]
Unfortunately, interruptions in my work have continued to be frequent. Still, it is progressing and is the sole pleasure incident to this strangely burdened existence of mine.—I have now begun the orchestration and by the end of this month a large portion of the first act will, I hope, be delivered complete to you. [...]
Source: Letters of Richard Wagner, Vol. 2, selected and ed. Wilhelm Altmann, trans. M. M. Bozman (J. M. Dent & Sons, 1927), No. 535