וַיְהִ֗י בִּימֵי֙ שְׁפֹ֣ט הַשֹּׁפְטִ֔ים וַיְהִ֥י רָעָ֖ב בָּאָ֑רֶץ וַיֵּ֨לֶךְ אִ֜ישׁ מִבֵּ֧ית לֶ֣חֶם יְהוּדָ֗ה לָגוּר֙ בִּשְׂדֵ֣י מוֹאָ֔ב ה֥וּא וְאִשְׁתּ֖וֹ וּשְׁנֵ֥י בָנָֽיו׃
사사들의 치리하던 때에 그 땅에 흉년이 드니라 유다 베들레헴에 한 사람이 그 아내와 두 아들을 데리고 모압 지방에 가서 우거하였는데
Kitzur Ba'al HaTurim
A man went. This appears twice in Scripture, here, and the second time (Ruth 1:1): “Now it came to pass in the days when the judges judged, that there was a famine in the land, and a man went from Bethlehem of Judah to sojourn in the fields of Moav.” As a result of “a man went,” the first redeemer (Moshe) was born, and by means of the latter “a man went,” the last redeemer, who is the Mashiach, the son of David, will come.
Radak
שדה אדום, a synonym for “the land of Edom.” We have the same synonym also being used for the land of Moav in Ruth 1,1 when Elimelech left the land of Israel to settle in שדה מואב, meaning in ארץ מואב.
Rashi
Ruth, Psalms, Job etc – Ruth was first, in the "days the judges judged" (Ruth 1:1). Psalms David said, and he was before Job according to the one who says it was in the days of the Queen of Sheba, and that was after the three books of Shlomo.