The Bible gives the answer to these two questions in Ezekiel 36.
“(1) “As for you, son of man, prophesy to the mountains of Israel, and say: ‘O mountains of Israel, hear the word of the LORD! (2) This is what the sovereign LORD says: The enemy has spoken against you, saying “Aha!” and, “The ancient heights have become our property!” (3) So prophesy and say: ‘This is what the sovereign LORD says: Surely because they have made you desolate and crushed you from all directions, so that you have become the property of the rest of the nations, and have become the subject of gossip and slander among the people, (4) therefore, O mountains of Israel, hear the word of the sovereign LORD: This is what the sovereign LORD says to the mountains and hills, the ravines and valleys, and to the desolate ruins and the abandoned cities that have become prey and an object of derision to the rest of the nations round about– (5) therefore this is what the sovereign LORD says: Surely I have spoken in the fire of my zeal against the rest of the nations, and against all Edom, who with great joy and utter contempt have made my land their property and prey, because of its pasture.’ (6) “Therefore prophesy concerning the land of Israel, and say to the mountains and hills, the ravines and valleys, ‘This is what the sovereign LORD says: Look, I have spoken in my zeal and in my anger, because you have endured the insults of the nations. (7) So this is what the sovereign LORD says: I vow that the nations around you will endure insults as well. (8) “‘But you, mountains of Israel, will grow your branches, and bear your fruit for my people Israel; for they will arrive soon. (9) For indeed, I am on your side; I will turn to you, and you will be plowed and planted. (10) I will multiply your people–the whole house of Israel, all of it. The cities will be populated and the ruins rebuilt. (11) I will increase the number of people and animals on you; they will increase and be fruitful. I will cause you to be inhabited as in ancient times, and will do more good for you than at the beginning of your history. Then you will know that I am the LORD. (12) I will lead people, my people Israel, across you; they will possess you and you will become their inheritance. No longer will you bereave them of their children. (13) “‘This is what the sovereign LORD says: Because they are saying to you, “You are a devourer of men, and bereave your nation of children,” (14) therefore you will no longer devour people and no longer bereave your nation of children, declares the sovereign LORD. (15) I will no longer subject you to the nations’ insults; no longer will you bear the shame of the peoples, and no longer will you bereave your nation, declares the sovereign LORD.’” (16) The word of the LORD came to me: (17) “Son of man, when the house of Israel was living on their own land, they defiled it by their behavior and their deeds. In my sight their behavior was like the uncleanness of a woman having her monthly period. (18) So I poured my anger on them because of the blood they shed on the land and because of the idols with which they defiled it. (19) I scattered them among the nations; they were dispersed throughout foreign countries. In accordance with their behavior and their deeds I judged them. (20) But when they arrived in the nations where they went, they profaned my holy name. It was said of them, ‘These are the people of the LORD, yet they have departed from his land.’ (21) I was concerned for my holy reputation which the house of Israel profaned among the nations where they went. (22) “Therefore say to the house of Israel, ‘This is what the sovereign LORD says: It is not for your sake that I am about to act, O house of Israel, but for the sake of my holy reputation which you profaned among the nations where you went. (23) I will magnify my great name that has been profaned among the nations, that you have profaned among them. The nations will know that I am the LORD, declares the sovereign LORD, when I magnify myself among you in their sight. (24) “‘I will take you from the nations and gather you from all the countries; then I will bring you to your land. (25) I will sprinkle you with pure water and you will be clean from all your impurities. I will purify you from all your idols. (26) I will give you a new heart, and I will put a new spirit within you. I will remove the heart of stone from your body and give you a heart of flesh. (27) I will put my Spirit within you; I will take the initiative and you will obey my statutes and carefully observe my regulations. (28) Then you will live in the land I gave to your fathers; you will be my people, and I will be your God. (29) I will save you from all your uncleanness. I will call for the grain and multiply it; I will not bring a famine on you. (30) I will multiply the fruit of the trees and the produce of the fields, so that you will never again suffer the disgrace of famine among the nations. (31) Then you will remember your evil behavior and your deeds which were not good; you will loathe yourselves on account of your sins and your abominable deeds. (32) Understand that it is not for your sake I am about to act, declares the sovereign LORD. Be ashamed and embarrassed by your behavior, O house of Israel. (33) “‘This is what the sovereign LORD says: In the day I cleanse you from all your sins, I will populate the cities and the ruins will be rebuilt. (34) The desolate land will be plowed, instead of being desolate in the sight of everyone who passes by. (35) They will say, “This desolate land has become like the garden of Eden; the ruined, desolate, and destroyed cities are now fortified and inhabited.” (36) Then the nations which remain around you will know that I, the LORD, have rebuilt the ruins and replanted what was desolate. I, the LORD, have spoken–and I will do it!’ (37) “This is what the sovereign LORD says: I will allow the house of Israel to ask me to do this for them: I will multiply their people like sheep. (38) Like the sheep for offerings, like the sheep of Jerusalem during her appointed feasts, so will the ruined cities be filled with flocks of people. Then they will know that I am the LORD.”” (Ezek 36:1–38 NET)