Please explain the quote "out of this body of his, out of his own loins, life!" from chapter two of The Good Earth, by Pearl S. Buck.
The Good Earth, by Pearl S. Buck, is set China and its protagonist is a poor farmer named Wang Lung. He wants a wife to do the household chores while he works in the fields; however, he is so poor that the only woman he can afford to marry is a former slave named O-lan.
Wang-Lung does not love his wife, but he admires her efficiency and her good work ethic. Once she has caught up on the all the neglected and necessary chores in the house, O-lan joins her husband and works at his side in the fields. Here they have a kind of symmetry and purpose which they do not necessarily share inside the house. As they worked,
[t]here was only this perfect sympathy of movement, of turning this earth of theirs over and over to the sun, this earth which formed their home and fed their bodies and made their gods.... Some time, in some age, bodies of men and women had been buried there, houses had stood there, had fallen, and gone back into the earth. So would also their house, some time, return into the earth, their bodies also. Each had his turn at this earth. They worked on, moving together—together—producing the fruit of this earth.
Soon after she begins working in the fields, O-lan tells her husband that she is pregnant. Just as it is an amazing thing for Wang Lung to produce a harvest from his labors in the field, so it is an amazing thing for him to think about having produced a child. With wonder, he thinks about it:
out of this body of his, out of his own loins, life!
Together they tilled the land and produced the "fruit of this earth," and together they created another kind of life, a new "fruit," in the form of a son.