Reference for Ketubot 221:4

ואתכם אזרה בגוים, "And you I will scatter among the nations." This verse is best explained in conjunction with what we have learned in Ketuvot 111 that G'd made the (Jews) people swear three (two) oaths at the time they went into exile.. 1) they would not try and recapture the land of Israel by force of arms; 2) they would not start a rebellion against their host countries while in exile. 3) G'd made the nations swear that they would not oppress the Jews excessively. In our verse the Torah alludes to two things. The word אזרה alludes to the oath not to try and recapture the land of Israel by force. The word בגוים refers to the oath not to start a rebellion against the host countries. The words והריקותי אחריכם חרב, "I will draw out the sword after you," is a threat that if the Israelites do not abide by the oaths mentioned G'd would make their lives הפקר, abandoned property. The words והיתה ארצכם שממה "your land will be waste-land," is the reason why G'd has to scatter the Israelites among the nations. Otherwise He could not fulfil His decree for the land to rest by not being worked and thus make up for the failure of the Jewish people to observe the שמטה years while they occupied the land. This is also why the Torah emphasises that all this would happpen while the Jewish people are in exile, i.e. ואתם, "as for you."