What advise does herbert offer about magwitch? Why does he say Pip should wait to tell Magwitch that he cannot accept his money?

The next morning, Magwitch tells the young men his story. He was an orphaned child and lived a life of crime out of necessity. His earliest memory is of stealing turnips to feed himself. As a young man, he met a gentleman criminal named Compeyson and fell under his power. Compeyson had already driven another accomplice, Arthur, into alcoholism and madness. Arthur, Magwitch says, was driven to despair by the memory of a wealthy woman he and Compeyson had once victimized. Magwitch remembers a woman from his own past and becomes distraught, but he does not tell Herbert and Pip about her. He continues, saying that when he and Compeyson were caught, Compeyson turned on him, using his gentleman’s manners to obtain a light sentence at the trial. Magwitch wanted revenge, and Compeyson was the man Pip saw him struggling with that night on the marsh.

At this point, Herbert passes Pip a note that tangles the situation even further. The note reveals that Arthur was Miss Havisham’s half brother; Compeyson was the man who stood her up on their wedding day.