In its biblical context, Ruth’s pledge echoes formulaic language for a covenant or a treaty in the Bible and the ancient Near East. It evokes divine utterances such as “They shall be My people, and I will be their God” (Jer. 32:38; also 31:33). It also recalls words uttered by King Jehoshaphat of Judah when speaking to Israelite kings who invited him to join forces (1 Kings 22:4 and 2 Kings 3:7); the similarity is even greater in 2 Chron. 18:3, which is a parallel account to 2 Kings 3:7.(Tikva Frymer-Kensky, “Ruth on the Royal Way,” in Reading the Women of the BibleBHS: New Interpretations of Their Stories (New York: Schocken, 2002)
Mark Smith compares Ruth’s pledge with Hittite and Ugaritic treaties, as well as the above cited references to 1 and 2 Kings, to highlight the similarities in language and concepts. Smith disagrees with Campbell’s conclusion that Ruth “brings the lofty concept of covenant into vital contact with day-to-day life, not at the royal court or in the temple, but right here in the narrow compass of village life.” (Campbell, J., Edward F. (2008). Ruth: A new translation with introduction, notes, and commentary.)
Instead, Smith considers covenant language to exist at all levels of society, with royal treaties capitalizing on familiar metaphorical constructions.
(Mark S. Smith, “ ‘Your People Shall Be My People’: Family and Covenant in Ruth 1:16–17,” CBQ 69 (2007): 242–58, 254.)
The closest and most revealing analogy to Ruth’s vow (1:16–17) is that of another foreigner in the Bible who swears loyalty to a Judahite of Bethlehem, namely Ittai the Gittite. When King David flees Jerusalem after his son usurps the throne, Ittai comes to join and support him. David, sounding much like Naomi, attempts to deter Ittai, saying: “Why should you too go with us? Go back [shuv] and stay with the new king, for you are a foreigner and you are also an exile from your country. You came only yesterday; should I make you wander about with us today, when I myself must go wherever I can? Go back [shuv], and take your kinsmen with you, in true faithfulness [ḥesed] (2 Sam. 15:19–20). Like Naomi, David also uses the key word shuv, “return” or “go back,” in his urging. But like Ruth, Ittai refuses to turn back. Instead he vows to link his fate with David’s: “As the Lord lives and as my lord the king lives, wherever my lord the king may be, there your servant will be, whether for death or for life!” (15:21). In both these instances, a foreigner leaves the comfort of home and joins a wandering Judean.
The comparison suggests an altruistic motive for both. Each places the welfare of the other person ahead of self-interest.
Two important differences highlight the distinctiveness of Ruth’s gesture in contrast to Ittai’s: first, as a widow, Ruth goes to Judah with only the impoverished Naomi as a familiar companion, whereas Ittai is accompanied by his men and presumably his wealth. More importantly, Ittai has made a commitment to a king, even if this is a king on the run. There is a prospect of some reward when the wheel of fortune turns. In contrast, Ruth has linked herself to a person of no standing, who seems to be going back to nothing and (according to Naomi in Ruth 1:21) with nothing, having to fend for herself alone.
Most Rabbinic traditions understand that Ruth’s vow signifies her conversion. The Rabbinic sages also provide a motive for it: Naomi’s piety was so impressive that Ruth longed to follow her and learn from her. The Targum explains Ruth’s reason for following with Naomi: “for I desire to become a proselyte.…” The Targum then presents each part of Ruth’s declaration as a point-by-point response to a specific teaching by Naomi (see below for details), a tradition evident in several sources (e.g., Ruth R. 2.20; B. Yev. 47b; also Rashi on 1:16–17, where the same process unfolds but Naomi’s statements differ). These additions amplify the extent to which Ruth commits herself to Israel’s traditions. But none of this appears in the text. Rather, the plain sense implies that what propels Ruth is her unwillingness to abandon Naomi (see comment at 1:16). Her love for Naomi exemplifies the Torah’s teaching about loving the stranger (Lev. 19:33–34; Deut. 10:19), for in Moab, Naomi is the stranger.
Ruth’s status after her vow is subject to discussion. Although most early Jewish sources consider this dialogue an act of conversion (Targum; Ruth R. 2.22; Ruth Z. 12), Ruth continues to be called a “Moabite,” with no hint that her status has changed. Glover, who examines the processes of conversion in Ruth from an ethnological perspective, suggests that Ruth’s declaration can only be seen as a step in the process. Ethnographic studies indicate that changing affiliation cannot be enacted unilaterally but requires communal consent, and the Book of Ruth, Glover shows, charts such a process (even if the notion of conversion was not as yet current at the time of Ruth)
(.N. Glover, “Your People, My People: An Exploration of Ethnicity in Ruth,” JSOT 3 (2009): 293–313.)
thanks to Jewish Publication Society.