מדרש על רות 3:18

“She said: Sit, my daughter, until you know how the matter will develop, as the man will not rest unless he finishes the matter today” (Ruth 3:18).
“She said: Sit, my daughter.” Rabbi Huna [said] in the name of Rabbi Shmuel bar Rav Yitzḥak: The righteous, their yes is yes and their no is no, as it is stated: “As the man will not rest unless he finishes the matter today.”