Behar 

בהר

The commandment to observe the Sabbatical Year, i.e., the prohibition against working the land during the seventh year of the agricultural cycle, appears in this Torah portion. The Sages provide a rationale for this commandment, and characterize as mighty those who observe the Sabbatical Year. 

A certain student came and said to Rav Huna: What is the reason for the Sabbatical Year? Rav Huna said to him…The Holy One, blessed be He, said to the Jewish people: Sow for six years and refrain during the seventh, so that that you will know that the land is Mine. “Mighty in strength, who do His bidding, heeding His word” (Psalms 103:20)…. Rabbi Yitzhak said: This verse is speaking of those who observe the Sabbatical Year. Typically, a person observes a commandment for an hour or for a day, but is one ever asked to observe a commandment for a year? And the Israelites observe this commandment for a year. <source>(Sanhedrin 39a; Midrash Tehillim [Buber] 103) </source>