What was happening?
Solomon had finished building the temple and prayed a long prayer of dedication. Read 2 Chronicles 6. Part of it asked what should happen when the rain stopped because the people had sinned.
26“When the heavens are shut up and there is no rain because they have sinned against You, when they pray toward this place and confess Your name, and turn from their sin because You afflict them,
27then hear in heaven, and forgive the sin of Your servants, Your people Israel, that You may teach them the good way in which they should walk; and send rain on Your land which You have given to Your people as an inheritance.
What did God say?
12Then the LORD appeared to Solomon by night, and said to him: “I have heard your prayer, and have chosen this place for Myself as a house of sacrifice.
13When I shut up heaven and there is no rain, or command the locusts to devour the land, or send pestilence among My people,
14if My people who are called by My name will humble themselves, and pray and seek My face, and turn from their wicked ways, then I will hear from heaven, and will forgive their sin and heal their land.
God answers the prayer Solomon had prayed. The drought, locusts and pestilence in verse 13 are the troubles Solomon named. The healing of the land is the answer to them: rain, harvest and health in the land God had given Israel.
19“But if you turn away and forsake My statutes and My commandments which I have set before you, and go and serve other gods, and worship them,
20then I will uproot them from My land which I have given them; and this house which I have sanctified for My name I will cast out of My sight, and will make it a proverb and a byword among all peoples.
The promise comes with a warning. If the people turned to other gods, they would be uprooted from the land and the temple itself would be cast off. Both halves belong to the covenant God made with Israel.
How do Christians apply it today?
Christians differ here. Some pray the verse over their own nation. Others point out that no modern nation stands where Israel stood under that covenant, and apply it to the church, God's people in every nation. Many draw a broader principle from it: God answers humble repentance with mercy.
Where most agree is on the order. The call goes first to “My people who are called by My name”. It begins with God's own people humbling themselves and turning from their own wrongs, before anyone else's.
For example: “Lord, we are Your people. Forgive us where we have gone our own way. Teach us to humble ourselves, pray and seek Your face, and have mercy on the place where we live. Amen.” This is a prepared example.
For a method you can use with any verse, read how to read a Bible verse in context. For the whole book, see our guide to 2 Chronicles.