Ruth 4:11
And all the people that were in the gate, and the elders, said, We are witnesses. The LORD make the woman that is come into thine house like Rachel and like Leah, which two did build the house of Israel: and do thou worthily in Ephratah, and be famous in Beth-lehem:
All the people in the gate with the elders witnessed Boaz taking Ruth to be his wife and blessed her to be like Rachel and Leah who built the house of Israel, wishing him prosperity in Ephrathah and renown in Bethlehem. The blessing belongs to the completion of the kinsman-redeemer's duty in public at the gate, where Boaz bought all that was Elimelech's and Chilion's and Mahlon's and took Ruth the Moabitess to raise up the name of the dead upon his inheritance after the nearer kinsman refused and yielded his right by drawing off his shoe. Building a house means bringing sons into a family, for a house is a family and not merely a building, so the prayer was that Ruth would bear children and help establish a family as Rachel and Leah had done. Their union produced Obed, ancestor of David and through David's line of Christ, so Ruth the Moabitess became one of the progenitors of the Lord according to the flesh. The near kinsman is a type of the Lord, fulfilled when Christ became man's blood-relative by taking human flesh to redeem people and their lost inheritance, and to be the everlasting head whose people share His enduring life and make David's house stand forever.
Witnesses and Wedding Blessing
All the people that were in the gate together with the elders witnessed Boaz's marriage to Ruth. They blessed Ruth to become like Rachel and like Leah, the two who built the house of Israel through the part they took in building it up. They wished prosperity and renown in Ephrathah and Bethlehem, praying that the couple would prosper there and that Boaz would do worthily and become famous in Bethlehem. Bethlehem is also called Ephratah.
Marriage is shown to be a public and formal occasion conducted with witnesses, pledges, and a covenant. Its customs included ceremony and the presence of friends, as seen in the account of Ruth 4:9-13.
The word rendered witnesses uses in the Septuagint the identical Greek term martus or martur that is elsewhere translated martyr. That usage proves its primitive meaning is simply one who witnesses to what he has seen and heard.
Redemption, House, and Christ
Ruth 4:1-12 belongs to the account of kinship-based redemption, in which the redemption of a person, an inheritance, or freedom from bondage that its owner could not recover belonged to the nearest blood-relative who was able to redeem. The verse records the public completion of the Go'el's duty at the city gate, where the elders and the people as witnesses affirmed that Boaz had bought all that was Elimelech's and Chilion's and Mahlon's from Naomi and had taken Ruth the Moabitess, the wife of Mahlon, to be his wife to raise up the name of the dead upon his inheritance so it would not be cut off. Raising up seed for a kinsman who died without issue was the specific duty of the nearest kinsman as Go'el, not of a brother only. Boaz lawfully assumed it after the nearer kinsman refused lest he mar his own inheritance and transferred his right by drawing off his shoe, with redemption of the land bound together with marriage to the widow.
The book is a pastoral account of home life among Israel showing God's care for the Seed, and the near kinsman is a type of the Lord. This establishes the pattern fulfilled when Christ became humanity's blood-relative by taking human flesh and being able to redeem people and their lost inheritance. Building a house means bringing a son into a family, for a house means a family and not merely a building. Rachel and Leah built the house of Israel through the children born to them, so the elders' blessing asks that Ruth bear children and help establish a family. This sense of house as family explains how David's house could continue through a son.
Following Boaz's purchase of the family inheritance and commitment to preserve the dead man's name through Ruth, their union produced Obed, ancestor of David and through David's line of Christ. So Ruth the Moabitess maiden became one of the progenitors of the Lord according to the flesh. Building David's house forever means giving it a head who remains forever and whose people share his enduring life, which is fulfilled in Christ, David's descendant and the everlasting head of his people.