Boaz referred to Ruth as his "daughter." Obviously, this is not the case literally, but it may be an indicator of their age difference and perhaps the reason why he was reluctant to pursue his romantic concern for her. Additionally, the fact he mentioned that Ruth did not seek a younger man proves that Boaz considered himself to be significantly older. It likely also indicates that Ruth had, in her youthful beauty, an appeal which would have attracted such suitors had she desired them. Boaz stated that Ruth had shown great kindness to him by making this request of him instead of pursuing a younger man closer to her age.
Boaz made an oath--"as the LORD lives"--to fulfill his obligation if he could legally do so. The law imposed the duty upon the closest male relative to marry the childless widow and raise up a son for her dead husband. But, the law also allowed him to renounce this responsibility if he would take upon himself the disgrace connected with such a refusal (Deut. 25:5-10). Since there was a man who was a closer relative to Elimelech's family than Boaz was, that man would be legally given the right to take Ruth under his wing, if he so desired. Boaz would only be able to fulfill her request if that nearest relative forfeited his right in this matter.
"So she lay at his feet until morning, and she arose before one could recognize another. Then he said, 'Do not let it be known that the woman came to the threshing floor.' Also he said, 'Bring the shawl that is on you and hold it.' And when she held it, he measured six measures of barley, and laid it on her. Then she went into the city. When she came to her mother-in-law, she said, 'Is that you, my daughter?' Then she told her all that the man had done for her. And she said, 'These six measures of barley he gave me; for he said to me, "Do not go empty-handed to your mother-in-law."' Then she said, 'Sit still, my daughter, until you know how the matter will turn out; for the man will not rest until he has concluded the matter this day'" (Ruth 3:14-18).
Both Boaz and Ruth are up before daybreak to insure their reputations. Boaz doesn't want any rumors spreading. This precaution would not have been as significant had Boaz been the closest relative to Elimelech's family. For Ruth to be seen carrying a load of gleanings at that hour would not have looked suspicious. This gift of barley to Ruth (and Naomi) showed Boaz's wisdom in helping her return home as well as his thoughtful kindness.
When Ruth returned to Naomi, she detailed what happened. Ruth was instructed by her mother-in-law to "sit still". Was Ruth nervous, fidgety, and full of excitement? Most likely this was the case, and there was nothing more they could do at that time except wait.