The Talmud states that the descendants of Joseph are immune to the evil eye, citing the verse 'a fruitful vine by a spring' (Genesis 49:22), and explains this as meaning they transcend the domain of the eye. This passage establishes that ayin hara has a domain of influence that can be escaped.
רַבִּי יוֹחָנָן הֲוָה רְגִיל דַּהֲוָה קָא אָזֵיל וְיָתֵיב אַשַּׁעֲרֵי דִטְבִילָה. אֲמַר: כִּי סָלְקָן בְּנוֹת יִשְׂרָאֵל וְאָתְיָין מִטְּבִילָה, מִסְתַּכְּלָן בִּי, וְנֶהֱוֵי לְהוּ זַרְעָא דְּשַׁפִּירֵי כְּווֹתִי. אָמְרִי לֵיהּ רַבָּנַן: לָא קָא מִסְתְּפֵי מָר מֵעֵינָא בִּישָׁא? אֲמַר לְהוּ: אֲנָא מִזַּרְעָא דְּיוֹסֵף קָא אָתֵינָא, דְּלָא שָׁלְטָא בֵּיהּ עֵינָא בִּישָׁא, דִּכְתִיב ״בֵּן פּוֹרָת יוֹסֵף בֵּן פּוֹרָת עֲלֵי עָיִן״, וְאָמַר רַבִּי אֲבָהוּ: אַל תִּקְרֵי ״עֲלֵי עָיִן״, אֶלָּא ״עוֹלֵי עָיִן״. רַבִּי יוֹסֵי בְּרַבִּי חֲנִינָא אֲמַר מֵהָכָא: ״וְיִדְגּוּ לָרֹב בְּקֶרֶב הָאָרֶץ״, מָה דָּגִים שֶׁבַּיָּם מַיִם מְכַסִּין עֲלֵיהֶם וְאֵין עַיִן הָרָע שׁוֹלֶטֶת בָּהֶם, אַף זַרְעוֹ שֶׁל יוֹסֵף אֵין עַיִן הָרָע שׁוֹלֶטֶת בָּהֶם. וְאִי בָּעֵית אֵימָא: עַיִן שֶׁלֹּא רָצְתָה לִזּוֹן מִמַּה שֶּׁאֵינוֹ שֶׁלּוֹ — אֵין עַיִן הָרָע שׁוֹלֶטֶת בּוֹ.
Similarly, the Gemara relates that Rabbi Yoḥanan was accustomed to go and sit at the gates of the women’s immersion sites. Rabbi Yoḥanan, who was known for his extraordinary good looks, explained this and said: When the daughters of Israel emerge from their immersion, they will look at me, and will have children as beautiful as I. The Sages asked him: Master, do you not fear the evil eye? He said to them: I descend from the seed of Joseph over whom the evil eye has no dominion, as it is written: “Joseph is a bountiful vine, a bountiful vine on a spring [alei ayin]” (Genesis 49:22). “Ayin” can mean both “spring” and “eye.” And Rabbi Abbahu said a homiletic interpretation: Do not read it alei ayin, rather olei ayin, above the eye; they transcend the influence of the evil eye. Rabbi Yosei, son of Rabbi Ḥanina, cited a different proof, from Jacob’s blessing of Joseph’s sons, Ephraim and Menashe: “The angel who redeems me from all evil shall bless the young and in them may my name be recalled, and the name of my fathers, Abraham and Isaac, and may they multiply [veyidgu] in the midst of the earth” (Genesis 48:16). Veyidgu is related etymologically to the word fish [dag]. Just as the fish in the sea, water covers them and the evil eye has no dominion over them, so too the seed of Joseph, the evil eye has no dominion over them. And if you wish, say instead: Joseph’s eye, which did not seek to feast on that which was not his, Potiphar’s wife, the evil eye has no dominion over him.