Isaiah 44

1. YET now hear, O Jacob my servant; and Israel, whom I have chosen:

When he chose to follow God, his name was Jacob. When the Lord called him up, he received a new name, Israel.
There are two parts to your discipleship – both the servant and the master choose each other, and can work together. It is a dual commitment.

3. For I will pour water upon him that is thirsty, and floods upon the dry ground: I will pour my spirit upon thy seed, and my blessing upon thine offspring:

The Lord gives the right amount to those who require it, pouring water on the thirst, while a ground that is dry needs a lot more.

4. And they shall spring up as among the grass, as willows by the water courses.

The effects of the water (v3) are here.

5. One shall say, I am the LORD's; and another shall call himself by the name of Jacob; and another shall subscribe with his hand unto the LORD, and surname himself by the name of Israel.

The effects of the spirit upon the offspring (v3) are here as well, with the same principle of joint work (v1) repeated here as well. There will be those who choose, and those who are chosen.
It's also talking about missionary work and conversion.