Reference for Sotah 70:13

כמאן אזלא הא דתניא (דברים כא, י) ושבית שביו לרבות כנענים שבחוצה לארץ שאם חוזרין בתשובה מקבלין אותן

The third set was that which he caused to be erected in Gilgal, as it is said: And those twelve stones which they took.<span class="x" onmousemove="('comment',' Josh. IV, 20. ');">¹⁰</span> Our Rabbis taught: How did the Israelites inscribe the Torah? — R. Judah says: They inscribed it upon the stones, as it is stated: 'Thou shalt write upon the stones all the words of this law etc.' After that they plastered them over with plaster. R. Simeon said to him, According to your explanation, how did the nations of that period learn the Torah!<span class="x" onmousemove="('comment',' Since the inscription was covered with plaster. ');">¹¹</span> — He replied to him, The Holy One, blessed be He, endowed them with exceptional intelligence; and they sent their scribes who peeled off the plaster and carried away [a copy of the inscription]. On that account was the verdict sealed against them [to descend] to the pit of destruction, because it was their duty to learn [Torah] but they failed to do so. R. Simeon says: They inscribed it upon the plaster and wrote below, That they teach you not to do after all [their abominations].<span class="x" onmousemove="('comment',' Deut. XX, 18. The command to destroy was limited to those of the seven nations who resided in Canaan. Those of them who lived outside its borders could survive by giving up their abominable practices. ');">¹²</span> Hence you learn that if they turn in penitence they would be accepted. Raba b. Shila said: What is R. Simeon's reason? — Because it is written: And the peoples shall be as the burnings of lime<span class="x" onmousemove="('comment',' Isa. XXXIII, 12. The word for 'lime' is the same as for plaster. ');">¹³</span> — i.e., on account of the matter of the plaster.<span class="x" onmousemove="('comment',' The nations will be destroyed because they neglected to pay heed to the teachings inserted on the plaster. ');">¹⁴</span> And [how does] R. Judah [explain this verse]? — [Their destruction will be] like plaster — as there is no other remedy for plaster except burning, so there is no other remedy for those nations [who cleave to the abominations] except burning. According to whom [is the following teaching] which has been taught: And thou carriest them away captive<span class="x" onmousemove="('comment',' Deut. XXI, 10. ');">¹⁵</span> — this is to include Canaanites who reside outside the land [of Israel] so if they turn in penitence they will be accepted.

Jastrow