The word "privately" indicates that he was alone with his disciples. AT: "Later, when he was alone with his disciples, he turned to them and said" (See: [[rc://en/ta/man/translate/figs-explicit]])
This probably refers to the good works and miracles that Jesus was doing. AT: "How good it is for those who see the things that you see me doing" (See: [[rc://en/ta/man/translate/figs-explicit]])