He actually wrote 2 of those. For the sake of education, let’s provide the complete text of one (via deepl.com):

spoiler

Lick my a… right already, lick it nice and clean, lick it clean, lick my a… That’s a greasy desire, only well lubricated with butter, the licking of the roast my daily do. Three lick more than two, go ahead, take the test and lick, lick, lick. Everyone licks his own a…

The phrase, aka the Swabian Salute, had been popularized a few years earlier in Goethe’s quite successful play Götz von Berlichingen. It is the knight’s reply to a demand for surrender. Götz may be more famous for his “iron fist/iron hand”, a prosthetic hand. Two prosthetics that are thought to have belonged to him, may be seen in a museum.