אמרתי אפאיהם, "I had said: 'I will consign them to the most remote corner.'" "I will scatter them to the ends of the globe.⁠"
According to Nachmanides, the words mean that God says: "I had originally wanted that they remain scattered to the corners of the globe forever so that their memory will be blotted out among mankind.⁠"This is an allusion to the exile of the Ten Tribes who were exiled to the region of the river Gozan, (Kings II 17,6) the river referred to by our sages as Sabatyon. (according to Sanhedrin 65 Sambatyon) The word גוזן is related to ויגז שלוים, Numbers 11,31 "it (the wind) swept quail.⁠" We also encounter the a similar word in Psalms 71,6 כי אתה גוזי, "for You were my support.⁠" The people standing on the far side of that river are effectively removed from human society (no one can cross the river). The river is called Sabatyon because it stops flowing on the Sabbath. In the language of the people in that region the word סבט is equivalent to our word שבת. In Arabic too, the Sabbath is called סבט. It is a custom among those people to append the ending יון to many words, hence the name סבטיון. Nachmanides furnishes examples of other words with that ending.
Even though, at this stage, the Torah speaks here in riddles, allusions, and in a very abbreviated form, we can find illuminating comments by our sages on the subject scattered throughout the Talmud and Midrashim. For instance, in Bereshit Rabbah 73,6 Rabbi Yehudah son of Rabbi Seymon says that the tribes of Yehudah and Binyamin were not exiled to the same areas as were the Ten Tribes who had been exiled long before beyond the river Sabatyon, whereas the tribes of Yehudah and Binyamin were scattered all over the globe.
In Midrash Shir Hashirim Zutta 1,16 the words אף ערשנו רעננה are understood by the Midrash as an allusion to these Ten Tribes who were exiled beyond the river Sabatyon.
The Jerusalem Talmud Sanhedrin 10,8 writes that there were three exiles of the Israelites (the northern kingdom, I presume, Ed.); 1) beyond the river Sabatyon, 2) the exile somewhere close to Antiochya; 3) an exile which was preceded by a cloud descending and hiding the people being exiled. Just as the Ten Tribes (actually 7) were exiled in three stages and to three locations, the two and a half Tribes on the East Bank of the Jordan who were the first to be exiled also were exiled in three stages. The source from which we derive all this is Ezekiel 23,31: בדרך אחותך הלכת ונתתי כוסה בידך, "seeing you walked the same path as your sister, therefore I placed her cup in your hand.⁠" Just as the exile was divided into three episodes and locations, so the eventual return to the Holy land will follow a similar pattern The sages base this on Isaiah 49,9: "tell the prisoners 'get going;'" this (part of) the verse applies to the exiles from beyond the river Sabatyon. The second half of the verse in Isaiah which reads: "to the ones who were exiled in darkness,⁠" applies to the people exiled beyond the Sabatyon. The next section of the verse i.e. the words: "show yourselves!⁠" refers to the exiles who had been mysteriously swallowed by the cloud; The final words of that verse, i.e. "they shall pasture along the roads,⁠" apply to the group of exiles who had been taken to somewhere near Antiochya.
In the Tosephta of Sanhedrin (chapter 13) we have been taught in the name of Rabbi that the Ten Tribes will enjoy a share in the world to come. He bases himself on Isaiah 27,13: "it will be on that day (the day described in verse 12) that a great shofar will be sounded and the strayed who are in the land of Assyria and the expelled in the land of Egypt shall come and worship the Lord on the holy mount, in Jerusalem.⁠" The peoples mentioned are the ones we know as the "Ten Tribes.⁠" According to Sifra Bechukotai 8 the reference is to the people described in Leviticus 26,38. Rabbi Akiva says that the reference is to the Ten Tribes who have been exiled to the land of the Medes.