Isaiah 55:10-11 speaks of God giving rain (which is analogous to seed) to the sower. Here's a breakdown of the purpose:
* To Produce Bread (Food): God provides the rain so that the earth yields crops, ultimately providing food for people to eat.
* To Fulfill God's Purpose: God's word (represented by the rain) will not return to Him empty but will accomplish what He purposes and succeed in the thing for which He sent it.
In context of the entire passage Isaiah 55:1-13, the giving of seed (rain) to the sower symbolizes God's abundant provision (both physical and spiritual) and His intention to bring about fruitful results in people's lives.