Sifrei on Deuteronomy
כי עם קדוש אתה לה' א-להיך. קדושה שהיא עליך היא גרמה לך.
(Devarim 14:2) "For a holy people are you to the L-rd your G-d": The holiness that is upon you has caused you to become a chosen people to Him.
(ד"א, לא תגרום לעם אחר להיות קדוש.
(Ibid. 18:5) "For in him (the Cohein) did the L-rd your G-d choose from all of your tribes to stand and minister in the name of the L-rd, he and his sons all of the days."
כיוצא בו, כי בו) [בך] בחר ה'. [כמ"ש] כי יעקב בחר לו י-ה, להיות לו לעם סגלה, ישראל לסגולתו.ד"א, כי עם קדוש אתה. קדושת עצמך.
Similarly (Psalms 135:4) "For Yaakov has the L-rd chosen for Himself, Israel, as His chosen one."
ובך בחר ה' א-להיך להיות לו לעם סגלה מכל העמים. מלמד שכל אחד ואחד מישראל, [חביב] לפני הקב"ה ככל אומות העולם.
Variantly: "For a holy people are you": (even) more than your forefathers.
יכול אף מאבות הראשונים? ת"ל מכל העמים אשר על פני האדמה, אמור מעתה, משלפניו ומשלאחריו; ולא מאבות הראשונים.[ד"א, לא תגרום לעם אחר להיות קדוש כיוצא בך].
"and in you has the L-rd chosen": your own holiness. "to be unto Him a chosen people from all of the peoples": We are hereby taught that each one of the just is beloved by the Holy One Blessed be He as all of the gentiles (together). I might think, even more than the early fathers (Avraham, Yitzchak, and Yaakov). It is, therefore, written "from all the peoples that are on the face of the earth," i.e., from one end of the earth to the other, and not (that they are more beloved) than the first fathers. Variantly: "from all the peoples": and do not cause another people to become holy.