It was narrated that 'Amir bin Wathilah said: "A man asked 'Ali" Did the Messenger of Allah used to tell you anything in secret that he did not tell the people?' Ali got so angry that his face turned red, and he said: 'He used not to tell me anything in secret that he di8d not tell the people except that he told me four things when he and I were alone in the house. He said: Allah curses the alone who curses his father, Allah curses the one who offers a sacrifice to anyone other than Allah, Allah curse the one who gives refuge to an offender and Allah curses the one who changes boundary markers."" (Sahih)