Shmita and Yovel שמיטה ויובל
The seventh year of the land's rest and the fiftieth year of release — commandments binding the people to the Land.
Once in seven years the land of Israel rests: no sowing, no pruning, no harvesting as an owner. Whatever grows of itself is ownerless, available to all, including animals. Debts are released the same year. The Torah answers the obvious question in advance — «what shall we eat in the seventh year?» — with the promise of a threefold sixth-year crop.
After seven cycles comes the yovel: the shofar sounds on Yom Kippur, slaves go free, and land returns to the families that first held it. A field cannot be sold outright — «for the land is Mine»; only the crops until the jubilee are sold. Yovel applied only while all the tribes sat on their portions.
The count of shmita years began fourteen years after entering the Land, in 2503. The Talmud ties the seventy years of exile to unkept shmita years.