Why did she give this Brachah?
Vilna Gaon: She thought that they want that she will bestow to them Chesed, since they were good to her when they were her daughters-in-law. Therefore, she told them that they will not benefit from going after her. She cannot do Chesed with them. Rather, Hashem will do with them.
What is the significance of "l'Veis Imah"?
Malbim: If they return to Mo'av, they can live in any city of Mo'av, or return to their mothers' houses. She advised the latter. Just like you clung to me, for I was like a mother to you, it is better to return to your true mothers.
Some say that Rus and Orpah had already converted. How could Na'ami suggest that they return to their mothers' houses [and live like Nochriyos]?!
Tzitz Eliezer (17:42, citing the Ben Ish Chai): They should persist to guard Jewish law 1 . However, if you go to Eretz Yisrael now, you will not be guarded on the road. People will suspect that you were defiled on the way 2 . Return to your mothers' houses; if you want to come to Beis Lechem, Hashem will arrange a way that you can come guarded, without any suspicion.
Tzitz Eliezer: How can he explain verse 15, in which Na'ami tells Rus to return to her nation and gods?! Refer to 1:15:3:1-3 and the notes there.
If they remain in Mo'av, will people not suspect this? Mo'av said, we cannot guard "Lo Sin'af", for we come from Zenus - "va'Taharenah Shtei Venos Lot me'Avihen" (Bereishis 19:36)' (Devarim Rabah Ekev DH me'Eimasai)! (PF)
What is the significance of "Ka'asher Asisem Im ha'Mesim v'Imadi"?
Vilna Gaon: For Chesed with the deceased, one does not expect payment from the Mes. So with me, do not expect payment from me - I am an Ani, who is like a Mes!
Malbim: You already did even Chesed with me, and more, also with the Mesim, and also in their lifetimes, they were good to their husbands. They made shrouds for the Mesim, and pardoned their Kesuvos to Na'ami (Rus Rabah 2:14). The laws of Mo'av are that the Mes is buried from his estate, and they collect their Kesuvos from the estate 1 . They pardoned this due to Chesed. Surely Hashem will do Chesed with you - He will not deny the reward due to you according to your Chesed!
Do Nochrim have Kesuvos? Also, a mother does not inherit her sons! (Perhaps she would have inherited them based on the custom in Mo'av. - PF) Etz Yosef (on the Midrash) - "Im ha'Mesim" implies Chesed in death, and not in their lifetimes. Na'ami said "Imadi" after this, implying that the Chesed with her was after that with the Mesim. She was a guarantor for their Kesuvos, and they exempted her.
