When the death penalty is prescribed but no mode, the mode can be inferred by the principle of Gezerah Shawah - comparing similar or analogous expressions in two or more passages, in one of which the meaning and import of the expression are unmistakable. Regarding "a wizard" the law says (Lev. 20:27), "They shall stone them with stones; their blood shall be upon them." Here the expression "Demehem bam" is plainly used in connection with death by stoning; hence it is argued that, wherever the same expression occurs in the Pentateuch in connection with the death penalty, it means death by stoning, and consequently the punishment of the crimes mentioned in Lev. 20:9, 11, 12, 13, 16, is the same: death by stoning.
- Wilhelm Bacher and Lewis N. Dembitz, Capital Punishment, Jewish Encyclopedia (1901), at http://www.jewishencyclopedia.com/view.jsp?artid=128&letter=C.