Jamieson, Fausset and Brown on Hosea 2:21

21. in that day--of grace to Israel.

heavens ... hear the earth--personification. However many be the intermediate instruments, God is the Great First Cause of all nature's phenomena. God had threatened (Ho 2:9) He would take back His corn, His wine, &c. Here, on the contrary, God promises to hearken to the skies, as it were, supplicating Him to fill them with rain to pour on the earth; and that the skies again would hearken to the earth begging for a supply of the rain it requires; and again, that the earth would hearken to the corn, wine, and oil, begging it to bring them forth; and these again would hear Jezreel, that is, would fulfil Israel's prayers for a supply of them. Israel is now no longer "Jezreel" in the sense, "God will SCATTER" (Ho 1:4), but in the sense, "God will PLANT" (Ho 1:11).