Messiah (mâšîah, "the anointed one"): Jewish religious concept, a future savior who will, in some sense, come to restore Israel. Both the nature of the Messiah and the restoration were matters of debate.
Roots of the concept: the messianic psalms
In the book of Psalms we find many ancient Jewish songs. It is hard to date them; in its present form, the book of Psalms postdates the Babylonian Captivity of the Jews (587-539) and may have served as the hymnbook of the "second Temple" (i.e., the Temple between 539 BCE and 70 CE). However, there are many indications that the core of the book of Psalms is much older, and a case can be made for the antiquity of the "royal psalms" (songs referring to the king).
Psalm 18 expresses royal gratitude after an escape from enemy hands; in Psalms 21 and 60, the monarch rejoices in God's strength after a victory; Psalm 61 asks for God's blessing. Since the king was anointed, all these songs might in a sense be called "messianic". However, some of these royal psalms describe an idealized ruler, and these are sometimes termed the "messianic psalms" par excellence. For example, the second Psalm describes not a historical coalition against the Jews, but is a very general description of God's effective dealing with the enemies of the king of the Jews.
Why do the nations conspire and the peoples plot in vain? The kings of the earth take their stand and the rulers gather together against the Lord and against His anointed one. "Let us break the chains," they say, "and throw off the fetters." The One enthroned in heaven laughs; the Lord scoffs at them. Then He shall rebuke them in anger and terrifies them in his wrath, saying, "I have installed My king on Zion, my holy hill."
I will proclaim the decree of the Lord: He said to me, "You are My son, today I have become your father. Ask of Me, and I will make the nations your inheritance, the ends of the earth your possession. You will rule them with an iron scepter; you shall dash them to pieces like pottery."note[Psalm 2.2-9.]
Texts like these were certainly not uncommon in the ancient Near East. The Egyptian pharaohs claimed descent from the sun god Ra and boasted how they -with a little help of the gods- defeated all enemies of order and truth. The Persian Behistun inscription belongs to the same category. The sentiments can also be found in Psalm 20:
I know that the Lord saves his anointed; He answers him from His holy heaven with the saving power of His right hand. Some trust in chariots and some in horses, but we trust in the name of the Lord our God. They [the enemies in chariots and on horses] are brought to their knees and fall, but we rise up and stand firm. O Lord, save the king! Answer us when we call!note[Psalm 20.6-9.]
Another idealized description of the kings' behavior can be found in the following song, which was written to celebrate a royal wedding. The king or crown prince is addressed as follows:
Gird your sword upon your side, o mighty one; clothe yourself with splendor and majesty. In your majesty ride forth victoriously on behalf of truth, humility and righteousness; let your right hand display awesome deeds. Let your sharp arrows piece the hearts of the king's enemies; let the nations fall beneath your feet. Your throne, o God, will last for ever and ever; a scepter of justice will be the scepter of your kingdom. You love righteousness and hate wickedness; therefore, God, your God, has set you above your companions by anointing you with the oil of joy.note[Psalm 45.3-7.]
After these words, which were addressed to the groom, the composer goes on to tell about the beauty of the bride and advises her to forget her own country and father's home, now that she has found such a fine husband. Although the song must have been written for one particular wedding, the king's portrait is highly idealized. The same ideas can be found in Psalm 72, but that song should probably be dated later.
Psalm 110 is a very remarkable text, because the vision of the destruction of the enemies is now proclaimed in a priestly, not-royal context. This may signify that the song is very old (because king David acted as priest); but it can also point to a date after the Babylonian Exile, when the high priests were Israel's worldly leaders.note[Jesus seems to have been puzzled by this text: Mark 12.35-37.]
The Lord says to my lord: "Sit at my right hand until I make your enemies a footstool for your feet."
The Lord will extend your mighty scepter from Zion; you will rule in the midst of your enemies. "Your troops will be willing on your day of battle. [...]"
The Lord has sworn and will not change His mind: "You are a priest for ever, in the order of Melchizedek."
The Lord is at your right hand; he will crush kings on the day of his wrath. He will judge the nations, heaping op the dead and crushing the rulers of the whole earth.note[Psalm 110.1-6.]
Summing up, we may conclude that the book of Psalms contains several songs about an idealized anointed ruler who will destroy the enemies of Israel on behalf of justice and righteousness. In Psalm 2, the idealized ruler is called the "son of God". The same idea is expressed in Psalm 18.50 and 89.26. The motif seems to be very old indeed, because it can be found in the following prophecy by the prophet Nathan, who reported to David a divine promise regarding Solomon:
The Lord declares to you that the Lord Himself will establish a house for you. When your days are over and you rest with your fathers, I will raise up your offspring to succeed you, who will come from your own body, and I will establish his kingdom. He is the one who will build a house for My name [i.e, the Temple], and I will establish the throne of his kingdom forever. I will be his father, and he shall be My son. When he does wrong, I will punish him with the rod of men, with floggings inflicted by men. But My love will never been taken away from him. [...] Your house and your kingdom shall endure for ever before Me; your throne shall be established for ever.note[2 Samuel 7.11b-16.]
All these texts were written at different moments and we may not simply compare them. However, we can be sure that stories and poems similar to those quoted above were current in the late seventh, early sixth century BCE, when the first messianic speculations started.