“It was taught, Rabbi El’azar ha-Qappar said: Let one always pray to be spared this fate [of poverty], for if he does not descend his son will, and if not his son, his grandson, for it is said, בִּגְלַל (bigelal), because for this thing (Deuteronomy 15:10). The School of Rabbi Yishma’el taught: It is a גַלגַל (galgal), wheel, that revolves in the world” (BT Shabbat 151a).
“Seeing a גוּלגוֹלֶת (gulgolet), skull, floating on the water, [Hillel] said: ‘Because you drowned others, they drowned you, and those who drowned you will themselves eventually be drowned'” (M Avot 2:7).
“Rabbi Yirmeyah son of Abba said in the name of Rabbi Yoḥanan, ‘Whoever walks four cubits in the land of Israel is assured to be a son of the world to come.’ Now… aren’t the righteous outside the Land going to be revived?—Rabbi Il’a said, ‘By גִּלְגּוּל (gilgul), rolling.’ Rabbi Abba Sala the Great objected, ‘Rolling will be painful to the righteous!'” (BT Ketubbot 111a, cf. Zohar 1:113b-114b [MhN], 131a).
“And this is the mystery of גִּלְגּוּל (gilgul), rolling: The גַלגַל (galgal), wheel, does not move without the flow of water through the conduit. Likewise, the conduit is the mystery of the letter ו (vav), by which the wheel is turned. And the secret of the matter is that just as the wheel will have no motion without the aqueduct, so too the wheel which is the letter י (yod) will have no rolling, without the aqueduct which is the letter ו (vav)… י (yod) is the point. ו (Vav) is [the conduit] of the wheel. And there is no movement in the wheel at the six spokes [the numerical value of ו (vav)], but only at the point” (Zohar 3:214b, Ra’aya Meheimna Pineḥas).