Verse 21. In that day - In the day of gospel-grace. I will hear - God the first and universal cause will influence the heavens, he will command their dew, and showers. When the earth is dry, it does as it were, cry to the heavens for refreshing showers, when the seed sown, the vines and olives planted, are at a stand, they cry to the earth for its kindly influences, that they may spring up, and yield fruit for Jezreel, which may call, and cry, but never will be satisfied if God does not hear them, and command his blessing which he promises to his people on renewing covenant with them. Now their repentance shall be blest with plenty, and God will set the frame of heaven and earth in due order to effect this; there shall be an harmony, between all subordinate causes moved by God the first great cause, whence expected events and fruits shall be produced for their good and comfort.
Verse 23. I will sow - I will bless them with a wonderful increase of people, exprest with allusion to seed sown in the earth. So the Jews multiplied after the Babylonish captivity, but much more are the numbers increased since the preaching of the gospel.