be inconstant

References in classic literature ?
An individual who is observed to be inconstant to his plans, or perhaps to carry on his affairs without any plan at all, is marked at once, by all prudent people, as a speedy victim to his own unsteadiness and folly.
Yates; and though he and Maria are very good friends, I think she likes Sotherton too well to be inconstant.
I will not allow it to be more man's nature than woman's to be inconstant and forget those they do love, or have loved.