Before Laertes returns to school in France, he gives his sister his last words of advice. He realizes that she and Hamlet have been getting closer, so he warns her against becoming too attached to Hamlet. Laertes reminds Ophelia of Hamlet's noble standing in Denmark; because he is the prince, he is not free to marry whom he chooses. Instead, he must keep the needs of his country ahead of his own.

He himself is subject to his birth.

He may not, as unvalued persons do,

Carve for himself, for on his choice depends

The safety and health of this whole state.

Laertes warns Ophelia that though Hamlet may act as though he loves her, it is not out of love but out of desire. He describes Hamlet's actions as temporary moments: just a short phase that the young prince is going through. He believes that once Hamlet gets what he wants from her, his attention will move on to someone else.

For Hamlet and the trifling of his favor,

Hold it a fashion and a toy in blood,

A violet in the youth of primy nature,

Forward, not permanent, sweet, not lasting,

The perfume and suppliance of a minute.

No more.

Therefore, Laertes thinks that it is best that Ophelia just stay away from Hamlet and ignore his flirtations. Because she is a dutiful sister, she listens to her brother and returns all of the gifts and letters Hamlet has sent her.

For a modern audience, Laertes's advice may seem strange, but Laertes worries that if his sister gives into Hamlet, her heart will be broken and her reputation ruined. His advice is intended to protect her from Hamlet.