Law and prophecy are the two great elements of the Jewish religion, and make it a direct divine introduction to Christianity, "the voice of him that crieth in the wilderness, Prepare ye the way of the Lord; make straight in the desert a highway for our God."
1. The law of Moses was the clearest expression of the holy will of God before the advent of Christ. The Decalogue is a marvel of ancient legislation, and in its two tables enjoins the sum and substance of all true piety and morality -- supreme love to God, and love to our neighbor. It set forth the ideal of righteousness, and was thus fitted most effectually to awaken the sense of man's great departure from it, the knowledge of sin and guilt.  8 It acted as a schoolmaster to lead men to Christ  that they might be justified by faith." 
The same sense of guilt and of the need of reconciliation was constantly kept alive by daily sacrifices, at first in the tabernacle and afterwards in the temple, and by the whole ceremonial law, which, as a wonderful system of types and shadows, perpetually pointed to the realities of the new covenant, especially to the one all-sufficient atoning sacrifice of Christ on the cross.
God in his justice requires absolute obedience and purity of heart under promise of life and penalty of death. Yet he cannot cruelly sport with man; he is the truthful faithful, and merciful God. In the moral and ritual law, therefore, as in a shell, is hidden the sweet kernel of a promise, that he will one day exhibit the ideal of righteousness in living form, and give the penitent sinner pardon for all his transgressions and the power to fulfil the law. Without such assurance the law were bitter irony.
As regards the law, the Jewish economy was a religion of repentance.
2. But it was at the same time, as already, hinted, the vehicle of the divine promise of redemption, and, as such, a religion of hope. While the Greeks and Romans put their golden age in the past, the Jews looked for theirs in the future. Their whole history, their religious, political, and social institutions and customs pointed to the coming of the Messiah, and the establishment of his kingdom on earth.
Prophecy, or the gospel under the covenant of the law, is really older than the law, which was added afterwards and came in between the promise and its fulfilment, between sin and redemption, between the disease and the cure.  Prophecy begins in paradise with the promise of the serpent-bruiser immediately after the fall. It predominates in the patriarchal age, especially in the life of Abraham, whose piety has the corresponding character of trust and faith; and Moses, the lawgiver, was at the same time a prophet pointing the people to a greater successor.  Without the comfort of the Messianic promise, the law must have driven the earnest soul to despair. From the time of Samuel, some eleven centuries before Christ, prophecy, hitherto sporadic, took an organized form in a permanent prophetical office and order. In this form it accompanied the Levitical priesthood and the Davidic dynasty down to the Babylonish captivity, survived this catastrophe, and directed the return of the people and the rebuilding of the temple; interpreting and applying the law, reproving abuses in church and state, predicting the terrible judgments and the redeeming grace of God, warning and punishing, comforting and encouraging, with an ever plainer reference to the coming Messiah, who should redeem Israel and the world from sin and misery, and establish a kingdom of peace and righteousness on earth.
The victorious reign of David and the peaceful reign of Solomon furnish, for Isaiah and his successors, the historical and typical ground for a prophetic picture of a far more glorious future, which, unless thus attached to living memories and present circumstances, could not have been understood. The subsequent catastrophe and the sufferings of the captivity served to develop the idea of a Messiah atoning for the sins of the people and entering through suffering into glory.
The prophetic was an extraordinary office, serving partly to complete, partly to correct the regular, hereditary priesthood, to prevent it from stiffening into monotonous formality, and keep it in living flow. The prophets were, so to speak, the Protestants of the ancient covenant, the ministers of the spirit and of immediate communion with God, in distinction from the ministers of the letter and of traditional and ceremonial mediation.
The flourishing period of our canonical prophecy began with the eighth century before Christ, some seven centuries after Moses, when Israel was suffering under Assyrian oppression. In this period before the captivity, Isaiah ("the salvation of God"), who appeared in the last years of king Uzziah, about ten years before the founding of Rome, is the leading figure; and around him Micah, Joel, and Obadiah in the kingdom of Judah, and Hosea, Amos, and Jonah in the kingdom of Israel, are grouped. Isaiah reached the highest elevation of prophecy, and unfolds feature by feature a picture of the Messiah -- springing from the house of David, preaching the glad tidings to the poor, healing the broken-hearted, opening the eyes to the blind, setting at liberty the captives, offering himself as a lamb to the slaughter, bearing the sins of the people, dying the just for the unjust, triumphing over death and ruling as king of peace over all nations -- a picture which came to its complete fulfilment in one person, and one only, Jesus of Nazareth. He makes the nearest approach to the cross, and his book is the Gospel of the Old Testament. In the period of the Babylonian exile, Jeremiah (i.e. "the Lord casts down") stands chief. He is the prophet of sorrow, and yet of the new covenant of the Spirit. In his denunciations of priests and false prophets, his lamentations over Jerusalem, his holy grief, his bitter persecution he resembles the mission and life of Christ. He remained in the land of his fathers, and sang his lamentation on the ruins of Jerusalem; while Ezekiel warned the exiles on the river Chebar against false prophets and carnal hopes, urged them to repentance, and depicted the new Jerusalem and the revival of the dry bones of the people by the breath of God; and Daniel at the court of Nebuchadnezzar in Babylon saw in the spirit the succession of the four empires and the final triumph of the eternal kingdom of the Son of Man. The prophets of the restoration are Haggai, Zechariah, and Malachi. With Malachi who lived to the time of Nehemiah, the Old Testament prophecy ceased, and Israel was left to himself four hundred years, to digest during this period of expectation the rich substance of that revelation, and to prepare the birth-place for the approaching redemption.
3. Immediately before the advent of the Messiah the whole Old Testament, the law and the prophets, Moses and Isaiah together, reappeared for a short season embodied in John the Baptist, and then in unrivalled humility disappeared as the red dawn in the splendor of the rising sun of the new covenant. This remarkable man, earnestly preaching repentance in the wilderness and laying the axe at the root of the tree, and at the same time comforting with prophecy, and pointing to the atoning Lamb of God, was indeed, as the immediate forerunner of the New Testament economy, and the personal friend of the heavenly Bridegroom, the greatest of them that were born of woman; yet in his official character as the representative of the ancient preparatory economy he stands lower than the least in that kingdom of Christ, which is infinitely more glorious than all its types and shadows in the past.
This is the Jewish religion, as it flowed from the fountain of divine revelation and lived in the true Israel, the spiritual children of Abraham, in John the Baptist, his parents and disciples, in the mother of Jesus, her kindred and friends, in the venerable Simeon, and the prophetess Anna, in Lazarus and his pious sisters, in the apostles and the first disciples, who embraced Jesus of Nazareth as the fulfiller of the law and the prophets, the Son of God and the Saviour of the world, and who were the first fruits of the Christian Church.
 Rom. 3:20: Dia nomou epignosis hamartias.  Paidagogos eis Christon  Gal. 3:24  Nomos parteiselthencame in besides, was added as an accessory arrangement, Rom. 5:20; comp. prosetethe the law was " superadded"to the promise given to Abraham, Galatians 3:19.  Deut. 18:15.
 Paidagogos eis Christon
 Gal. 3:24
 Nomos parteiselthencame in besides, was added as an accessory arrangement, Rom. 5:20; comp. prosetethe the law was " superadded"to the promise given to Abraham, Galatians 3:19.
 Deut. 18:15.