The Duke of Zhou said to his son, the Duke of Lu: “A leader does not neglect his relatives, nor does he give his ministers the opportunity to complain that his advice is not heeded. He does not dismiss old retainers without serious cause, nor does he demand all-round perfection in a single individual.”
The Duke of Zhou sent his eldest son Bo Qin (伯禽) to establish Confucius’s home state of Lu as part of his efforts to expand the domains of the Zhou Dynasty. He is said to have ruled there as the Duke of Zhou from 1042 to 997 BC.
There doesn’t seem to be any logical reason for including this passage unless it is simply to emphasize these strong historical ties. Still, the advice that the Duke gives his son is solid enough.