The ancients needed Rain Water when they were planting, and when they were sailing, they needed wind. Water and wind could arrive on time according to the seasons. The ancients called this natural phenomenon and order as faith. With faith, people can carry out productive labor and live a normal life. So they always sincerely pray to God or immortals to bless them so that they can get accurate and true faith. Later, people realized that human beings themselves need this kind of faith, and human trust needs to be guaranteed and realized by sincerity. Sincerity refers to an inner attitude, faith is the external expression of sincerity, sincerity and faith are two sides of one body.
passage?
Sincerity and faith are  two sides in one body.