Be all my sins remembered

In Hamlet, his 'To be or not to be...' ends with Hush you now, The fair Ophelia Nymph in thy orisons BE ALL MY SINS REMEMBERED.

Why would Hamlet want this?

Well, you list your sins in your prayers in order to beg that they be forgiven. Hamlet is in effect asking Ophelia to pray for forgiveness of his sins. (VSD)