What does sowing seeds mean biblically?

A man reaps what he sows. 

If he sows seed in the field of his lower nature, he will reap from it a harvest of corruption. 

But if he sows in the field of the Spirit, the Spirit will bring him a harvest of eternal life. 

So let us never tire of doing good, for if we do not slacken our efforts, we must in due time reap our harvest. Therefore, as opportunity offers, let us work for the good of all. 

—St Paul