Several places throughout the Talmud, we are taught that even though a particular halakhah might be derivable through the method of a “kal v’chomer”, nonetheless the Torah goes beyond and spells it out in a verse (tarach v’katav lah kra). Authorities debated whether this notion is extended to other derivational principles, such as gezeirah shavah or hekeish (see Mishneh L’Melekh, Malveh V’Loveh 4:1, Turei Even, notes to Rosh HaShanah 8a; Resp. Yabbia Omer III, Even HaEzer 14). Commentaries discuss why such a principle should exist; if, indeed, a halakhah can be derived through a kal v’chomer or some comparable method, it would seem that an additional verse would be unnecessary. The Pri Megadim takes this concept as indication that even though a given halakhah would have been known without an explicit verse, the existence of the verse strengthens the halakhah in some significant way. R. Yehoshua Baumol (Resp. Emek Halakhah, I, 45) suggests that the concept may impact on the scope of the notion of arevut, which mandates that Jews express responsibility for the spiritual well-being of other Jews. This obligation stems from the acceptance of such responsibility at the time of the giving of the Torah itself. Accordingly, he establishes in his discussion, the scope of this responsibility would extend only to concepts explicit in the Torah, and not to those that are derived through methodology such as kal v’chomer. Thus, “tarach v’katav lah kra” is necessary to include the relevant halakhah within the range of arevut.