Seder 108: Psalm 21---A Messianic Royal Psalm of Thanksgiving

 Psalm 21 is a royal psalm that can be seen as a sequel to Psalm 20.  Psalm 20 is a prayer for protection and success for the king, while Psalm 21 expresses the king's gratitude for the success that God has granted him.  

Here is one example of the connections between the two psalms:

Psalm 20:4---"May he grant you your heart's desire and fulfill all your plans!

Psalm 21:2---"You have given him his heart's desire...."

Psalm 21:1-7 shows gratitude for the promises of the Davidic covenant, including

• God's steadfast love (v.7; 2 Sam 7:15);
• God's presence (v. 6; 2 Sam 7:9);
• a dynasty lasting forever (vv 4, 6; 2 Sam 7:13, 16).

In verse 7 the king affirms his trust in God, rather than in horses or chariots(see 20:7).  Then in verses 8-13, the congregation affirms its faith in God's ulimate judgment of enemies and victory over all opposition.  The psalm begins and ends by praising God's strength. 

During the era of Solomon's Temple, this psalm could have been used to celebrate a victory or the anniversary of a king's coronation.  Then during the Second Temple period and beyond, it was natural to see this psalm messianically, especially with its references to eternal life and blessing (vv 4,6) and final victory.  The last half of the psalm reminds us of prophecies that the Messiah will conquer all enemies, including death (Isa 25:7-8; 1 Cor 15:54-57).

The Targum in verses 1 and 7 has "the king Messiah" for "the king,"  and the discussion of this psalm in Midrash Psalms is entirely about how the different parts of the psalm apply to the Messiah. Here are some examples of the discussion in Midrash Psalms:  

• The Midrash connects verse 2 ("you have given him his heart's desire and have not withheld the request of his lips") with Isa 11:4 ("he shall strike the earth with the rod of his mouth, and with the breath of his lips he shall kill the wicked").  
• To explain verse 4 ("he asked life of you"), it is speculated that the Messiah asked God for the resurrection of Korah and his colleagues, who were swallowed up by the ground during Israel's years in the wilderness (Num 16). 
• In connection with verse 6 ("you make him glad with the joy of your presence"), sages mention examples where the Messiah comes into the presence of God (Dan 7:13-14; Jer 30:21).  

Unlike some other royal psalms (45 and 110, e.g.), Psalm 21 is not referenced in the New Testament.  Some verses in Psalm 21 look like good candidates for a prosopological reading, but I am not aware of them being used in this way.  I may look into this question further.