According to the Sages, the phrase, “a time for throwing stones” is a reference to the destruction of Yerushalayim, when its grand walls were reduced to a heap of rocks. The phrase, “and a time to gather stones” refers to the second stage of exile, when King Yechonya, and those exiled with him, carried the stones and earth of Yerushalayim to Babylonia, in order to build synagogues and study halls from the precious and sacred earth of the Holy Land. Additionally, just as God allowed Yerushalayim to be destroyed and reduced to stones, He also allowed the stones to be gathered for Yerushalayim to be built once again.