Nothing is sillier than this charge of plagiarism. There is no sixth commandment in art. The poet dare help himself wherever he lists, wherever he finds material suited to his work. He may even appropriate entire columns with their carved capitals, if the temple he thus supports be a beautiful one. Goethe understood this very well, and so did Shakespeare before him.
Scintillations from the Prose Works of Heinrich Heine: I. Florentine Nights. II. Excerpts (ed. 1873)