The Jubilee in the Old Testament
The Sabbatical Year
The Jubilee Year
How it was Practiced
The Sabbatical Year

In addition to the consecration of time represented by the Sabbath, and the many festivals of Judaism (Passover, Tabernacles, etc.) there were Jewish institutions which consecrated entire years, the Sabbatical Year and the Jubilee Year.

Just as God asked for a weekly rest, or Sabbath, in his honor, he also asked for a Sabbath Year to be celebrated every seventh year. 

Lev 25:1-13 1The Lord said to Moses on Mount Sinai, 2 Say to the people of Israel, When you come into the land which I give you, the land shall keep a Sabbath to the Lord. 3 Six years you shall sow your field, and six years you shall prune your vineyard, and gather in its fruits; 4 but in the seventh year there shall be a Sabbath of solemn rest for the land, a Sabbath to the Lord;

Exodus 23:10-11 10"For six years you may sow your land and gather in its produce. 11But the seventh year you shall let the land lie untilled and unharvested, that the poor among you may eat of it and the beasts of the field may eat what the poor leave. So also shall you do in regard to your vineyard and your olive grove.

This was, therefore, no mundane year of rest but one consecrated to God, in which His Providence was depended upon for survival and His Lordship recognized in all areas of life. For example, the Sabbath year legislation provided for the restoration of freedom for those who in their need had sold themselves in servitude to their fellow Israelites. 

Exodus 21:2-6 2When you purchase a Hebrew slave, he is to serve you for six years, but in the seventh year he shall be given his freedom without cost. 3If he comes into service alone, he shall leave alone; if he comes with a wife, his wife shall leave with him. 4But if his master gives him a wife and she bears him sons or daughters, the woman and her children shall remain the master's property and the man shall leave alone. 5If, however, the slave declares, 'I am devoted to my master and my wife and children; I will not go free,' 6his master shall bring him to God and there, at the door or doorpost, he shall pierce his ear with an awl, thus keeping him as his slave forever.

And for the relaxation of debts for fellow Israelites.

Dt. 15:1-6 1"At the end of every seven-year period you shall have a relaxation of debts, 2which shall be observed as follows. Every creditor shall relax his claim on what he has loaned his neighbor; he must not press his neighbor, his kinsman, because a relaxation in honor of the LORD has been proclaimed. 3You may press a foreigner, but you shall relax the claim on your kinsman for what is yours. 4Nay, more! since the LORD, your God, will bless you abundantly in the land he will give you to occupy as your heritage, there should be no one of you in need. 5If you but heed the voice of the LORD, your God, and carefully observe all these commandments which I enjoin on you today, 6you will lend to many nations, and borrow from none; you will rule over many nations, and none will rule over you, since the LORD, your God, will bless you as he promised.