‘ And Ruth said, “Do not entreat me to leave you, and to return from following after you, for where you go, I will go, and where you lodge, I will lodge. Your people will be my people, and your God my God, where you die, I will die, and there will I be buried. YHWH do so to me, and more also (literally ‘and so may He add to do'), if anything but death parts you and me.”
Ruth firmly sets aside Naomi's arguments. She begs Naomi not to entreat her to leave her. Rather she wishes to share in all that Naomi will face in the future. She will go where she goes. She will lodge where she lodges. Naomi's people will be her people, and Naomi's God will be her God. She will die where Naomi dies, so much is she committed to Naomi's Israelite background. And she will be buried in the same land in which Naomi will be buried. The place where a person wished to be buried was a sign of the place that they saw as ‘home'. Thus this was thus a total commitment to being an Israelite. It was a reasonable position to take. By marrying a Yahwist she had already had to conform to Yahwism. And she would be looked on by many as an Israelite, because she had been incorporated into an Israelite family. The continued stress on the fact that she was a Moabite is mainly the author's, for to all intents and purposes to marry an Israelite and to commence worshipping YHWH and observing the Feasts was to become an Israelite (Exodus 12:48 - as a woman she would not require circumcision). It was happening all the time. Compare how Moses had married, first a Midianite, and then an Egyptian. The author is concerned to bring out that David had within him Moabite blood, but having said that, that it was the blood of someone who had chosen to be an Israelite and a Yahwist. It would be an encouragement to all foreigners (apart from Canaanites) who were considering becoming Yahwists, and would indicate to them that YHWH would accept them on equal terms and equally bless them.
Once again we have emphasis laid on the fact that by her decision Ruth, like her sister-in-law, was choosing which god she served. Indeed Ruth could have gone back with Naomi but have demanded to serve the god of Moab. But she committed herself to serving Naomi's God. This could only be because she had come truly to believe in YHWH. She wanted to be included in YHWH's covenant. As a wife she would have been expected to conform to the worship of her husband's God, even if she had retained aspects of her old religious life. But she could now have chosen to renege on her commitment to YHWH. Thus we see in Ruth a true believer to whom YHWH was very real, to such an extent that she was not willing to turn her back on Him..