Berith is the Hebrew word for covenant — one of the most important theological concepts in all of Scripture. It appears 287 times in the OT. A covenant is more than a contract; it involves the whole person in a binding, oath-sealed commitment. The cutting of animals in covenant ceremonies (Genesis 15) meant: "If I break this covenant, may what happened to these animals happen to me." God's covenants define His relationship with humanity.
The story of Scripture is the story of covenants. God's covenants with Noah (never to destroy the earth by flood), Abraham (land, seed, blessing), Moses (law at Sinai), David (an eternal throne), and the New Covenant (Jeremiah 31 / Jesus's blood at the Last Supper) form the backbone of redemptive history. Each covenant builds on the previous. The Hebrew word hesed (H2617, lovingkindness) is the character that keeps the covenant. The Greek equivalent is diatheke (G1242) — testament, covenant.