If I profane with my unworthiest hand
This holy shrine, the gentle sin is this:
My lips, two blushing pilgrims, ready stand
To smooth that rough touch with a tender kiss.
Romeo says that if his touch offends the holy shrine of Juliet's hand, he is willing to commit "the gentle sin" of kissing her hand to soothe any disrespect. Many editors emend "sin" to "fine," meaning "penalty" or "compensation." The reasoning for this change assumes that what Romeo says doesn't make sense, since Romeo is offering to make up for profaning the holy shrine of Juliet's hand by committing a "gentle sin." If Shakespeare meant to write "fine," not "sin," what Romeo says can be paraphrased this way: "If my rough hand has profaned the shrine that is your hand, I'm ready to make it up to you: my lips stand ready to smooth away my rough touch with a kiss."
However, it is quite as possible that Shakespeare did indeed mean to write "gentle sin." Here is an eloquent explanation of that point of view by James Bogle:
This [i.e., Romeo's speech] I take to mean:
"If I profane the holy shrine of your hand with my most unworthy hand, the noble 'sin' (if sin it be) is the ready availability of my lips, like two shy and blushing pilgrim travellers, to smooth over the rough touch of my hand upon yours by kissing your hand."
I don't therefore see "gentle sin" here as merely compensation or cure so much as a "sin which is not really a sin, since noble, which will prove its nobility by the pressing of lips to her hand to smooth over the rough touch of his hand" i.e., he likens to profanity the touching of her hand with his and then, anticipating that someone might comment that a kiss were more profane still, parries such a thrust by calling such a "sin" (if so it be) "noble" so that it be, in fact, at best, no sin, or at worst a much mitigated sin, particularly as it will communicate not only love for the maid but will smooth over (compensate or cure, if you like) the "rough touch" of his hand.
Juliet's reply is to gently chide his exaggerated feeling by saying that his hand is not so wrong to touch hers, since saints and palmers do as much, intimating, in effect, that a touch of the hand will suffice for the present, a kiss being premature (although she is soon enough persuaded otherwise).
