When your father is alive, observe his will. When your father is dead observe his former actions. If, for three years [after the death of your father] you do not change from the ways of your father, you can be called a 'real son (xiào/hsiao)'.
父在，觀其志；父殁，觀其行；三年无改於父之道，可謂孝矣。
Original text (Chinese)