A psalm of vision, reflection, observation, hope, prophecy and of salvation.
Psalm 89 seems to attribute the lyrics of its song solely to King David. That would be a correct surface-level observation, however it is important to remember that all of the Old Testament accounts, regardless of the literary genre, demonstrate types and shadows of the Coming Messiah, Jesus the Christ.
Dr. Christopher J. H. Wright says, “The Old Testament declares the promise that Jesus fulfills.” 
In a powerful sermon, I heard it preached, “The text of Scripture is not flat as one might imagine. There are peaks and valleys.” I would add – all of the landscape points to the redemptive work of the Messiah, reconciling a fallen, sinful humanity to a Holy God.
Let us explore how the landscape of the text of Psalm 89:20-37 points us to the redemptive work of Jesus the Messiah.
I have found David my servant; with my sacred oil I have anointed him.
David, the shepherd boy – the one whom at face-value was ridiculed by his own family as unworthy. Through the prophet Samuel the LORD God selected and publically anointed him to be the king of Israel.
Jesus, the Good Shepherd – the one whom at face-value was ridiculed by His own creation as unworthy. The LORD God publically anointed him with the Holy Spirit to begin His public ministry as King of Kings. 
We are reminded that God evaluates the heart, not the exterior. He calls and anoints those He deems worthy, regardless of the opinions of the world. 
My hand will sustain him; surely my arm will strengthen him.
The enemy will not get the better of him; the wicked will not oppress him.
Here we see the promise of God to sustain, protect and strengthen. This was evident in the life of King David. This was evident in the life and ministry of Christ Jesus.
We are reminded that regardless of the circumstances, trials, times of difficulty, valleys of darkness, moments of loneliness or any other situation life brings our way, our strength and sustenance comes from God alone. We have nothing to fear. 
I will crush his foes before him and strike down his adversaries. My faithful love will be with him, and through my name his horn will be exalted.
The psalmist prophesies, “his horn will be exalted.” This makes reference to strength and power. David’s strength did in fact become exalted far beyond his extensive military victories, in that his lineage extended directly to the foretold Messiah, Jesus the Christ. Look at the last portion of verse 24, and through my name. Through His name alone was David exalted. David did not act on his own might and abilities in order to increase anything lasting or substantial. This exaltation came directly through the power of THE NAME.
The strength and power of Jesus is without question headed towards the day when every nation, tribe and tongue will kneel before Him and confess His ultimate LORDSHIP. 
And I will appoint him to be my firstborn, the most exalted of the kings of the earth.
Jesus clearly fits this description in Paul’s letter to the church in Colossae, “The Son is the image of the invisible God, the firstborn over all creation” (Col 1:15 NIV).
I will maintain my love to him forever, and my covenant with him will never fail.
God’s covenant never failed the people of Israel. They failed Him over and over, but He always kept His end of the deal. The covenant God makes with anyone is binding, trustworthy and good. This held true with King David and holds true with His covenant relationship between each member of the Triune Godhead; God the Father, God the Son and God the Holy Spirit.
The covenant God the Father holds with Jesus is paramount to our eternal hope. Paul writes in his pastoral letter to Timothy, “This grace was given us in Christ Jesus before the beginning of time” (2 Tim 1:9).
You see, the covenant of grace through faith in Christ sets humanity up for eternal success. We cannot earn God’s favor in an of ourselves. We cannot do enough to pay the price for our sins. We cannot strive and toil and labor enough to fight against our guilty verdict. The price has been paid through Christ Jesus. Thanks be to God that Christ Himself intercedes on our behalf as our advocate! His covenant of love with the Father will never fail.
There are so many exciting nuggets of grace, hope, vision, and salvation contained within these few verses. I feel that the condensed packaging I’ve presented here only scratches the surface. An exhaustive study of the entirety of Psalm 89 could produce a good-sized book. I wanted to point out a few highlights to get your wheels turning.
When you look at something as simple as a psalm, remember it is the voice of God speaking through an inspired writer in the genre of poetry. While poetry has the potential to evoke emotions and to paint vivid imagery, in Scripture there is a greater purpose that points us towards the coming Messiah revealed within the pages of the New Testament.
 Christopher J. H. Wright, How to Preach &Teach the Old Testament for All Its Worth, p. 29.  1 Sam 16  Luke 3:22; Matt 3:16  1 Sam 16:7  Ps 56:11, 118:6; Heb 13:6  2 Sam 8; 1 Chr 18  Matt 1:6-16  Rom 14:11; Phil 2:10-11  Eph 2:8-9  Rom 8:34