Whoever tells a lie is not pure of heart, and such a person can not cook a clean soup.
Source, in full
To Mme. Streicher, in 1817, or 1818, after having dismissed an otherwise good housekeeper because she had told a falsehood to spare his feelings. in Beethoven: the Man and the Artist, as Revealed in his own Words by Ludwig van Beethoven, edited by Friedrich Kerst