Bundle of living – צרור החיים
The source of his term is from;
1 Samuel 25:29
”וְהָיְתָה נֶפֶשׁ אֲדֹנִי צְרוּרָה בִּצְרוֹר הַחַיִּים אֵת ה’ אֱלֹהֶיךָ“
“…then the life (Nefesh) of my master shall be bound in the bundle of the living with YHVH your God”
The sages explain that the bundle of living is the reward a man receives to be resurrected at the time of the Final Redemption.
Rabbi Chaim of Volozhin explains that this blessing is to elevate the Nefesh part of the soul, which is the lower part of the soul, to be connected with the higher parts, and through them, the root of the soul will be clinging to God (ELHYM).
It is common to see on tombstones the initials ת.נ.צ.ב.ה. It represents the blessings “May his soul be included in the bundle of living”.