Revelation 6:9
9 Now when the Lamb opened the fifth seal, I saw under the altar the souls of those who had been violently killed because of the word of God and because of the testimony they had given. 10 They cried out with a loud voice, “How long, Sovereign Master, holy and true, before you judge those who live on the earth and avenge our blood?” 11 Each of them was given a long white robe, and they were told to rest for a little longer, until the full number was reached of both their fellow servants and their brothers who were going to be killed just as they had been.
Avot D'Rabbi Natan 26:2
MishnahHe would also say: Do not hang around with cynics, for you may begin to learn from their ways. Do not break bread with an unlearned priest, for you may end up desecrating holy things. Do not break your vows, for you may come to break your oaths.1Oaths are more grave than vows, as he who swears a false oath in God’s name “will not be held guiltless” (Exodus 20:7). Do not accustom yourself to eating big meals, for you may end up having to eat scraps. Do not cause yourself to doubt, for you may then cause yourself to be overconfident. Do not leave the Land of Israel, for you may end up worshiping idols, just as David said (I Samuel 26:19), “For they have driven me out today, so that I cannot have a share in the Eternal’s inheritance, but am told to go and serve other gods.” Do you actually think King David would worship idols? Rather, David was saying that anyone who leaves the Land of Israel and goes to a foreign country, it is as if he were worshiping idols.He would also say: Anyone who is buried in any foreign country, it is as if he were buried in Babylon. Anyone who is buried in Babylon, it is as if he were buried in the Land of Israel. Anyone who is buried in the Land of Israel, it is as if he were buried underneath the altar, for all of the Land of Israel is fit for the altar. Anyone who is buried underneath the altar, it is as if he were buried under the Throne of Glory, as it says (Jeremiah 17:12), “A Throne of Glory, exalted from the beginning, is the place of our Sanctuary.”
Notes and References
"... In the Hebrew Bible the soul or spirit (nefesh, ruah) of a person, denoting both ‘breath’ and, more generally, ‘life-force’, is understood to be in God’s hands: ‘Into Your hand I entrust my spirit [ruhi]’ (Ps. 31:6); ‘In His hand is every living soul [nefesh kol hai], and the breath [ruah] of all mankind’ (Job 12:10). In later Jewish thought, in concert with belief in the continued existence of the soul after death, individual souls were often said to reside in a ‘treasury’ or ‘store-room’ (otsar) which is in proximity to, or ‘with’, God, as in the following midrashic comment on the phrase elohei haruhhot lekhol basar in Numbers 27:16 ..."
Mandel, Paul The Sacrifice of the Souls of the Righteous upon the Heavenly Altar: Transformations of Apocalyptic Traditions in Medieval Ashkenaz (pp. 49-72) Liverpool University Press, 2018