“If thou must love me, let it be for nought / Except for love's sake only.”
This quote has no known author and is recorded as an anonymous proverb.
About this quote
The sonnet asks the beloved to love her for nothing at all, not for her looks or her gentleness, and answers by promising that such a love can outlast every change in both of them. It is the verse form of a promise made to someone who may not be in the room.
Source: Sonnets from the Portuguese