VIOLA (CESARIO): You either fear his humour or my negligence, that you call in question the continuance of his love. Is he inconstant, sir, in his favours?
VALENTINE: No, believe me.

– William Shakespeare

Twelfth Night, Act 1, Scene 4. Viola wonders if Duke Orsino will continue treating her well as Cesario the pageboy, or if he is fickle in his favors. Valentine says he isn’t fickle.