Gilgil is another name for Resurrection

 Devarim (33:06)May Reuben live and not die, Though few be his numbers

Rabbeinu Bachya (Devarim 33:06) A kabbalistic approach: the word yechi  in the line refers to life in the hereafter. The words”won’t die”  refer to what would happen to Reuven as part of the system of the transmigration of souls, in order to spare him having to die a second time. This is the meaning of Onkelos’ translation of the words “won’t die. Onkelos revealed to us here that there is a transmigration of souls when the souls of people who committed certain sins reappear in another body to rehabilitate themselves by a second circuit of physical life on earth. This occurs after they had already once received their reward or punishment in the hereafter after having died, separated from the body which housed them originally This is a concept which is not hard to understand when one considers that the cycles of Shemittah years are something which repeat themselves time and again. A soul returns to a new habitat on earth after having received its initial judgment for how it performed on earth the first time around. According to many views expressed by our sages, this metamorphosis is what is known as “resurrection of the dead.” At any rate, considering both the comments of Onkelos in our verse and those of Targum Yonathan in Isaiah, it appears that the words of Moses about the tribe of Reuven are a prayer that they should live long enough so as not to need a second round of physical life on earth to rehabilitate themselves.