A correct answer is like an affectionate kiss.

[Eine richtige Antwort ist wie ein lieblicher Kuß.]

Johann Wolfgang von Goethe (1749-1832) German poet, statesman, scientist

Sprüche in Prosa: Maximen und Reflexionen [Proverbs in Prose: Maxims and Reflections] (1833) [tr. Mann (1948)]
    (Source)

See Proverbs 24:26.

(Source (German)). Alternate translation:

A right answer is like a loving kiss.
[tr. Stopp (1995), "Posthumous," "On Literature and Life," #888]