TT #175 · Parashas Shoftim · Fourth Aliyah · Passuk 18:11
Or a charmer of charms, or one who inquires of a ghost or a familiar spirit, or one who seeks the dead.
Torah Temimah points to Sanhedrin 65b.
TT lemma: וְיִדְּעֹנִי.
English: ‘And a familiar spirit’ – this is one who places a bone in his mouth (and speaks through it).
Derash defining the familiar spirit (Bavli) — a concrete description of the forbidden practice.
Consulting a familiar spirit (yidoni) by the described method is forbidden.