Psalm 118, with its repeated hopeful refrain that the LORD’s steadfast love endures forever, is important during Holy Week because:
- The crowds quoted Psalm 118 during the Triumphal Entry when they cried “hosanna” (Matthew 21:9, Mark 11:9-10).
- Jesus infuriated the Pharisees when he quoted Psalm 118 in the Parable of the Tenants (Matthew 21:33-46, cf. Mark 12:10, Luke 20:17, Acts 4:11, Ephesians 4:20).
- It is likely that Psalm 118 was the hymn that Jesus and the Disciples sang on Thursday night after the Last Supper before going out to the Mount of Olives.
Hosanna on Palm Sunday (Matthew 21:1-11). The crowds quoted to Psalm 118 in during the Triumphal Entry when they shouted “hosanna.”
 Now when they drew near to Jerusalem and came to Bethphage, to the Mount of Olives, then Jesus sent two disciples,  saying to them, “Go into the village in front of you, and immediately you will find a donkey tied, and a colt with her. Untie them and bring them to me.  If anyone says anything to you, you shall say, ‘The Lord needs them,’ and he will send them at once.”  This took place to fulfill what was spoken by the prophet, saying,
 “Say to the daughter of Zion,
‘Behold, your king is coming to you,
humble, and mounted on a donkey,
on a colt, the foal of a beast of burden.’”
 The disciples went and did as Jesus had directed them.  They brought the donkey and the colt and put on them their cloaks, and he sat on them.  Most of the crowd spread their cloaks on the road, and others cut branches from the trees and spread them on the road.  And the crowds that went before him and that followed him were shouting, “Hosanna to the Son of David! Blessed is he who comes in the name of the Lord! Hosanna in the highest!”  And when he entered Jerusalem, the whole city was stirred up, saying, “Who is this?”  And the crowds said, “This is the prophet Jesus, from Nazareth of Galilee.” (Matthew 21:1-11 ESV)
“Hosanna” appears only in the Old Testament is in Psalm 118:25. (See Piper’s article on Hosanna).
In Psalm 118, the words “save us” translate the Hebrew word “hosanna.” Hosanna carries the obvious meaning of a cry to God for help. But by the time we get to the Triumphal entry “hosanna” also carries the connotation of victory. We might paraphrase, “Our God will save us.”
Today we should cry out hosanna both as a petition for God to save us, but also triumphantly knowing that Jesus has won the decisive victory over death.
The Parable of the Tenants. Jesus references Psalm 118 in Matthew 21:42 in the Parable of the Tenants. The Pharisees perceived that Jesus was talking about them and did not appreciate it (Matthew 21:45-46).
 “Hear another parable. There was a master of a house who planted a vineyard and put a fence around it and dug a winepress in it and built a tower and leased it to tenants, and went into another country.  When the season for fruit drew near, he sent his servants to the tenants to get his fruit.  And the tenants took his servants and beat one, killed another, and stoned another.  Again he sent other servants, more than the first. And they did the same to them.  Finally he sent his son to them, saying, ‘They will respect my son.’  But when the tenants saw the son, they said to themselves, ‘This is the heir. Come, let us kill him and have his inheritance.’  And they took him and threw him out of the vineyard and killed him.  When therefore the owner of the vineyard comes, what will he do to those tenants?”  They said to him, “He will put those wretches to a miserable death and let out the vineyard to other tenants who will give him the fruits in their seasons.”
 Jesus said to them, “Have you never read in the Scriptures:
“‘The stone that the builders rejected
has become the cornerstone;
this was the Lord’s doing,
and it is marvelous in our eyes’?
 Therefore I tell you, the kingdom of God will be taken away from you and given to a people producing its fruits.  And the one who falls on this stone will be broken to pieces; and when it falls on anyone, it will crush him.”
 When the chief priests and the Pharisees heard his parables, they perceived that he was speaking about them.  And although they were seeking to arrest him, they feared the crowds, because they held him to be a prophet. (Matthew 21:33-46 ESV)
Jesus’s meaning was not lost on the Pharisees. He was identifying himself as the chief cornerstone and the Pharisees as the builders who rejected the chief cornerstone. Both Peter (1 Peter 2:7) and Paul reference our Lord’s exposition (Ephesians 2:20).
After the Last Supper. Matthew 26:30 tells us that, “And when they had sung a hymn, they went out to the Mount of Olives.” Given the place of Psalm 118 in Passover, it is likely that they sang Psalm 118 together including 118:22-24.
The stone that the builders rejected
has become the cornerstone.
This is the LORD’s doing;
it is marvelous in our eyes.
This is the day that the LORD has made;
let us rejoice and be glad in it.
Kidner writes these introductory paragraphs for the occasion of Psalm 118:
The stir of a great occasion lends its excitement to the psalm as it proceeds, and we become aware of a single worshipper at its centre, whose progress to the Temple to offer thanks celebrates no purely private deliverance like that of Psalm 116, but a victory and vindication worthy of a king. . .
As the final psalm of the ‘Egyptian Hallel’ sung to celebrate the Passover . . . this psalm may have pictured to those who first sang it the rescue of Israel at the Exodus, and the eventual journey’s end at Mount Zion. But it was destined to be fulfilled more perfectly, as the echoes of it on Palm Sunday and the Passion Week make clear to every reader of the Gospels.
 Kostenberger and Taylor, The Final Days of Jesus: The Most Important Week of the Most Important Person Who Ever Lived, 912.
 Derek Kidner, Psalms 73-150, ed. D.J. Wiseman, Tyndale Old Testament Commentaries (Downers Grove, IL: IVP, 1975), 412–413.
 Piper, “Hosanna!”
What Happened During Holy Week
John Piper’s Hosanna