The AnswerBy Rabbi Jack Abramowitz
Having described Israel’s rebellion and punishment in the previous chapter, G-d continues: I will avenge myself on the nations who unduly oppress Israel. I will return to Jerusalem, which will continue to be known as the city of truth and the Temple mount will again be known as the holy mountain. Old men and women will occupy the streets (meaning that the people will live to a ripe old age) and the streets will be filled with children playing (because of the great prosperity). “It will be wonderful in the eyes of the people and in My eyes,” says G-d, “how the righteous will resist temptation. I will save My people from their exiles, both east and west, and return them to Jerusalem where they will be My people. I will be their G-d in truth and in righteousness.“
G-d says: Let your hands be strong to rebuild the Temple; do not fear those who wish to prevent it. You will hear words of consolation from the mouths of the prophets. It used to be that there was no source of livelihood for a person and no peace from their enemies, and everyone would fight with their neighbors. But now, their planting is successful and their crops are a source of peace. The vine and ground give forth plentiful produce and Heaven gives forth its dew. G-d will cause the people who return to Jerusalem to enjoy these benefits.
It will be that just as the Jews were blamed by the other nations for the bad times, they will be credited by them for the good time and the nations will bless them for it. Be encouraged by the consolation because G-d has said that just as He punished their ancestors who rebelled against Him and did not repent, so will He reward this generation in Jerusalem. All they have to do is speak sincerely and in truth, seek compromises in arguments, and plan no evil for one another. (In this verse, G-d warns the Jews about sinas chinam, baseless hatred, which was ultimately the reason the second Temple was destroyed.)
Now G-d answers the question which was posed in the previous chapter, regarding whether fasts should continue to be observed after the second Temple is built. G-d says that the fasts of 17 Tamuz, 9 Av, Tzom Gedaliah, and 10 Teves will be a source of rejoicing in the time of the second Temple so long as the people love truth and peace. In the Messianic era, the people of many nations will come to Jerusalem to seek G-d and to pray to Him. When this happens, the Jews will be surrounded by throngs of people who wish to learn about G-d from them.