Deuteronomy 15:1
1 At the end of every seven years you must declare a cancellation of debts. 2 This is the nature of the cancellation: Every creditor must remit what he has loaned to another person; he must not force payment from his fellow Israelite, for it is to be recognized as “the Lord’s cancellation of debts.” 3 You may exact payment from a foreigner, but whatever your fellow Israelite owes you, you must remit.
Nehemiah 10:31
30 “We will not give our daughters in marriage to the neighboring peoples, and we will not take their daughters in marriage for our sons. 31 We will not buy on the Sabbath or on a holy day from the neighboring peoples who bring their wares and all kinds of grain to sell on the Sabbath day. We will let the fields lie fallow every seventh year, and we will cancel every loan. 32 We accept responsibility for fulfilling the commands to give one-third of a shekel each year for the work of the temple of our God, 33 for the loaves of presentation and for the regular grain offerings and regular burnt offerings, for the Sabbaths, for the new moons, for the appointed meetings, for the holy offerings, for the sin offerings to make atonement for Israel, and for all the work of the temple of our God.
Notes and References
"... [Sabbath] was not just a rest day. It was a religious day that belonged to Yahweh. Though more is made of the religious and cultic nature of the sabbath in texts outside the Pentateuch, there are indications in the Pentateuch that the day was a religious occasion. It was set apart or made holy to Yahweh. It was his day (Exodus 16:23, 25; 20:10; 31:15). Yet it was also a day holy for Israel (Ex 31:13). The command for Israel to participate in this day is linked to Israel’s being holy to the Lord, set apart to be his people. Thus in Exodus 31:12-17 the sabbath is a sign that Yahweh sanctifies Israel itself. Theologically, the day reminds Israel that Yahweh is Creator and Redeemer and Lord of all. Observance of the day at least implies an acknowledgment of the lordship of Yahweh. For an assessment of how, and if, Israel kept the sabbath day, texts outside the Pentateuch need to be consulted. For example, one can consult Psalm 92 and Ezekiel 46:1-3 regarding its celebration, Ezekiel 22 regarding the profaning of the sabbath as a factor leading to the exile, Nehemiah 10:31-33 for a commitment to keep the sabbath after the exile, and Judges 14:12-18; 1 Kings 8:65; 2 Kings 4:23; 11:5-9; 1 Chronicles 9:32; 23:31 for particular occurrences of the sabbath ..."
Alexander, T. Desmond, and David W. Baker Dictionary of the Old Testament: Pentateuch (p. 698) InterVarsity Press, 2003