Naomi and Ruth redeemed

Meanwhile Boaz went up to the town gate and sat down there just as the guardian-redeemer^[a] he had mentioned came along. Boaz said, “Come over here, my friend, and sit down.” So he went over and sat down.
² Boaz took ten of the elders of the town and said, “Sit here,” and they did so. ³ Then he said to the guardian-redeemer, “Naomi, who has come back from Moab, is selling the piece of land that belonged to our relative Elimelek. ⁴ I thought I should bring the matter to your attention and suggest that you buy it in the presence of these seated here and in the presence of the elders of my people. If you will redeem it, do so. But if you^[b] will not, tell me, so I will know. For no one has the right to do it except you, and I am next in line.”
“I will redeem it,” he said.
⁵ Then Boaz said, “On the day you buy the land from Naomi, you also acquire Ruth the Moabite, the^[c] dead man’s widow, in order to maintain the name of the dead with his property.”
⁶ At this, the guardian-redeemer said, “Then I cannot redeem it because I might endanger my own estate. You redeem it yourself. I cannot do it.”
⁷ (Now in earlier times in Israel, for the redemption and transfer of property to become final, one party took off his sandal and gave it to the other. This was the method of legalizing transactions in Israel.)
⁸ So the guardian-redeemer said to Boaz, “Buy it yourself.” And he removed his sandal.
⁹ Then Boaz announced to the elders and all the people, “Today you are witnesses that I have bought from Naomi all the property of Elimelek, Kilion and Mahlon. ¹⁰ I have also acquired Ruth the Moabite, Mahlon’s widow, as my wife, in order to maintain the name of the dead with his property, so that his name will not disappear from among his family or from his hometown. Today you are witnesses!”

In the end, Baoz did redeem Naomi, Ruth and their property. He kept his end of his promise. Even though he did not even make a promise. No where in the previous chapter did he say "i promise". Promises are of high importance and it is a covenant to God. 

Matthew 5:33-37

³³ “Again, you have heard what was said to your people long ago. They were told, ‘Do not break the promises you make to the Lord. Keep the oaths you have made to him.’ ³⁴ But here is what I tell you. Do not make any promises like that at all. Do not make them in the name of heaven. That is God’s throne. ³⁵ Do not make them in the name of the earth. That is the stool for God’s feet. Do not make them in the name of Jerusalem. That is the city of the Great King. ³⁶ And do not take an oath in the name of your head. You can’t make even one hair white or black.
³⁷ “Just let your ‘Yes’ mean ‘Yes.’ Let your ‘No’ mean ‘No.’ Anything more than this comes from the evil one.

When you say Yes, means Yes. No Means No. We do not have to make promises to others. When we say I will do it, means You would. Because that is sufficient. Promises are something serious, like a vow. Promises made in the name of God must be kept. God's name is not to be used loosely. Like stated in the 10 commandments, we should not use God's name in vain. Same for our promises, do not make promises to God in vain, just a simple Yes will do. 

Baoz redeemed the property and the 2 widows just like he had  said to Ruth. How many time have we broke our promises to someone? He did'nt.