“כִּי יַעֲקֹב בָּחַר לוֹ יָהּ יִשְׂרָאֵל לִסְגֻלָּתוֹ”
“For the LORD (YH) has chosen Jacob for Himself, Israel for His own possession (Segulah).”
The Zohar teaches us that three patriarchs Abraham, Isaac and Jacob are called Segulah because they created the channels of the Sefirot;
Chessed – Right – כהנים – Kohanim (priests)
Gevurah – Left – לויים – Levites
Tiferet – Central – ישראלים – Israelites
In this verse, God is represented by the short name of יה YH. This name is for Chokmah (Y י) and Binah (H ה). Jacob who was also named Israel represents the three columns. YH chose Israel for himself because they chose the Torah ways to be close to him.
The main difference between Israelites and the other nations is that they connected only to the Left column and the Israelites connect and draw from the three columns. The unification of the three columns is in Teferet, Jacob and is called Segulah.
“וְעַתָּה אִם שָׁמוֹעַ תִּשְׁמְעוּ בְּקֹלִי וּשְׁמַרְתֶּם אֶת בְּרִיתִי וִהְיִיתֶם לִי סְגֻלָּה מִכָּל הָעַמִּים כִּי לִי כָּל הָאָרֶץ”
“Now then, if you will indeed obey My voice and keep My covenant, then you shall be My own possession (Segulah) among all the peoples, for all the earth is Mine;”