Release or Sabbath Rest is now called Shemitah, coming from Leviticus and Deuteronomy:

Leviticus 25:1. And the LORD* spoke to Moses on Mount Sinai saying,

“Speak to the children of Israel, and say to them,

“When you come into the land which I AM giving to you, then the land will keep a Sabbath to the LORD*: 3. You will sow your field for six years, and for six years you will prune your vineyard and gather in its fruit, 4. But the seventh year will be a Sabbath of rest for the land, a Sabbath for the LORD*: you will neither sow your field nor prune your vineyard. 5. That which grows of its own accord of your harvest you will not reap, neither gather the grapes of your undressed vine for it is a year of rest for the land. 6. And the Sabbath produce of the land will be food for you, for you and for your servant, for your maid, for your hired servant, and for your stranger who lives with you, 7. And for your cattle and for the wild animals that are in your land, all its increase will be for food.”