The covenant God established with the nation of Israel at Mount Sinai through Moses (Exodus 19-24), expanded throughout the rest of the Pentateuch. Also called the Sinai Covenant or Old Covenant. Its core is the Ten Commandments (Exodus 20), surrounded by the Book of the Covenant (Exodus 21-23), the ceremonial law (Leviticus), and the civil statutes (Numbers, Deuteronomy). Structurally it resembles the Ancient Near Eastern suzerain-vassal treaty: historical prologue, stipulations, blessings and curses, witnesses, deposit in the ark.
The Mosaic covenant was bilateral: "If you will indeed obey my voice and keep my covenant, you shall be my treasured possession... but if you will not obey..." (Exod 19:5, Deut 28). Its purposes were multiple: (1) to reveal the character of God; (2) to mark Israel off as a holy nation among pagans; (3) to expose human sinfulness by spelling out God's standard (Romans 3:20 — "through the law comes knowledge of sin"); (4) to serve as a "tutor" or paidagōgos leading to Christ (Galatians 3:24); (5) to prefigure the gospel in its sacrificial system. Israel broke the covenant from the first Sabbath of its existence — hence the prophets' lament. The Mosaic law is not abolished; parts of it (the moral law reflected in the Decalogue) continue to bind universally, ceremonial law is fulfilled in Christ (Hebrews 8-10), and civil law served a typological purpose for Israel as a theocratic nation. Christians read Moses through Christ, not Christ through Moses — "the law was given through Moses; grace and truth came through Jesus Christ" (John 1:17).