A Sadducee came to Rabbi Abahu with a sharp question. "You rabbis teach," he said, "that the souls of the righteous are treasured up beneath the Throne of Glory. If that is so, how did the Witch of Endor summon the prophet Samuel from the dead? A soul safely filed under the throne cannot be whistled up by a necromancer" (1 Samuel 28).
Rabbi Abahu answered him without flinching.
For the first twelve months after death, he said, the soul is not yet fully at rest. The body, still nearly intact, remains a kind of anchor. The soul ascends and descends, ascends and descends, making its way slowly from this world to the next. During that year it can be reached. It can be summoned. It can even, in unusual cases, appear to the living.
But after twelve months the body is dissolved in the earth and the soul completes its ascent. After that, no witch, no medium, no king in disguise can call it back. The gate closes.
Samuel, Rabbi Abahu reminded the Sadducee, had been dead less than twelve months when Saul came to Endor in desperation. The timing was the loophole (Shabbat 152b).
The story is not a manual for necromancers. It is a rabbinic map of the afterlife: a year of transition during which the living and the dead are still close, and then a long silence in which the soul belongs wholly to God.