How can one bring salvation to souls in the underworld?

When a man lives in the world, filial devotion is his root of moral principle. 

The Book of Filial Devotion states “The ultimate filial devotion is to bring

recognition to one’s parents by leaving an honourable name forever through

establishing good virtues and practicing Tao.”  If we would like to achieve

perfect filial devotion, we should approach it in two ways.  When our parents

are alive, we must do our best not to confront them and respect them with

sincerity.  Once they pass away, we must bring salvation to them so that their

souls can transcend the cycle of birth and death and go to the Monastery of Heaven.

As a child or grandchild, how can we bring salvation to the souls of nine generations

of ancestors and seven generations of descendants in the underworld?  The answer

is one must be tenacious in practicing Tao, establish good virtues, accumulate merits

by doing good deeds, and keep the vows of adhering to Tao.  That is why there is

the saying “If one child receives Tien-Tao, nine generations of ancestors will be

honoured.  If one child attains Tao, nine generations of ancestors transcend the cycle

of birth and death from the underworld.”