19-21 Open to me the gates of righteousness, that I may enter through them and give thanks to the Lord. This is the gate of the Lord; the righteous shall enter through it. I thank you that you have answered me and have become my salvation. 22-24 The stone that the builders rejected has become the cornerstone. This is the Lord's doing; it is marvellous in our eyes. This is the day that the Lord has made; let us rejoice and be glad in it.

25 Save us, we pray, O Lord! O Lord, we pray, give us success! 26 Blessed is he who comes in the name of the Lord! We bless you from the house of the Lord. 27 The Lord is God, and he has made his light to shine upon us. Bind the festal sacrifice with cords, up to the horns of the altar! You are my God, and I will give thanks to you; you are my God; I will extol you. 29 Oh give thanks to the Lord, for he is good; for his steadfast love endures for ever! Psalm 118:22-29 English Standard Version

Psalms 113 to 118 were used to praise God during the major festivals of Israel, especially the Passover. It's said they were sung as the procession of worshippers moved to the temple, so vs 19-21 would have been appropriate as they approached the main gates. God's temple was a place of righteousness, and because God had become their salvation, the worshippers could now enter as those who were righteous. Verse 27 speaks of the ‘festal sacrifice’ that was made. But how much more true this is of what the gospel does for sinners. It’s because those who have believed on Christ have been made righteous through His perfect sacrifice, that they can confidently come into God's presence. Jesus is indeed our doorway.

Verses 22-24 would’ve had initial application to Israel's king, or to the whole nation itself. They had certainly been rejected by the nations around them, yet God had preserved them because He had chosen and appointed them to be the cornerstone of His plans for the world. But that plan would only find its fulfillment in the Messiah whom He was going to send. So does the New Testament confirm that?

Following the event when Jesus entered Jerusalem, not on a white steed - but humbly upon a donkey, and the crowds had sung His praise, Jesus went on to tell a story of a landowner who planted a vineyard and rented it to tenants. When harvest time came he sent servants to collect his fruit, but the tenants treated them all with contempt, even killing some. Eventually the owner sent his own son, but the tenants took him, threw him out of the vineyard, and killed him. When Jesus asked His hearers what they thought the owner would do, they replied “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.” (Matthew 21:41)

At that point, Jesus then quoted the words of vs 22-24 from today's Psalm, showing that He was the one whom the builders (the nation of Israel) rejected, but whom God had appointed to be the cornerstone of His kingdom. This is why the apostle Paul said to gentile Christians: “You are fellow citizens with God’s people and members of His household, built on the foundation of the apostles and prophets, with Christ Jesus Himself as the chief cornerstone.” (Ephesians 2:19-20) The apostle Peter also quoted the words of Christ being the cornerstone, and said: “The one who trusts in him will never be put to shame.” (1 Peter 2:6)

Despite the Psalm being about how God had saved them, what is asked for in vs 25?

They saw the need to continue to look to God for deliverance. The victories of the past didn’t mean they had no need of God's safekeeping in the future. Surely this is true of Christians too. Being 'saved' doesn't mean we don't need God's daily grace for the journey ahead. We will face many foes and battles along the way. Perhaps this is why Martin Luther, who was so used by God to turn people back to His word instead of following superstitions, said that this was his favorite Psalm. We need a foundation for our faith that is sure and certain, and that's what our Cornerstone is.

The Psalm finishes as it began – a heartfelt call to give thanks to the Lord, because He is good; and because His steadfast love endures for ever.