Halakhah su Deuteronomio 19:18

R. Ezekiel Landau, author of Teshuvot Noda bi-Yehudah employs this premise in explaining Rambam's position. Noda bi-Yehudah's elucidation of Rambam's position is formulated in the course of a responsum dealing with the divorce of Cleves. This responsum is also published in Or ha-Yashar, no. 27. Noda bi-Yehudah maintains that, even according to Rambam, a shoteh is exempt from mizvot only to the extent that his mental impairment interferes with rational fulfillment of such obligations. A person who is irrational in even a limited sense is exempt from any mizvah requiring an act which he cannot perform in a rational manner. Moreover, as noted earlier, any mizvah performed in an irrational manner is not deemed to constitute the fulfillment of an obligation. Nevertheless, such a person remains bound by any commandment which he can perform in a rational manner. However, a person who is to any extent exempt from mizvot by virtue of mental incompetence is excluded entirely from the category of qualified witnesses. The Gemara, Baba Kamma 88a, in establishing categories of qualified witnesses cites the verse "and behold, if the witness be a false witness and has testified falsely against his brother" (Deuteronomy 19:18). The phrase "his brother," (which certainly cannot be understood in a literal manner since no person's testimony is accepted for or against his brother) is understood by the Gemara as denoting "a brother in mizvot," i.e., a person equally bound by the commandments. Accordingly, the principle is established that a person who is not subject to the commandments is disqualified from serving as a witness. Noda bi-Yehudah argues that even if he behaves irrationally with regard to only one specific type of conduct, a shoteh is disqualified from serving as a witness even though he is exempt only from mizvot with regard to which such behavior serves as an impediment. Since such a person is bound by only a limited obligation regarding commandments he is not "a brother (i.e., an equal) with regard to commandments." According to Noda bi-Yehudah's analysis of Rambam's position, as distinct from that of Iggerot Mosheh, a person suffering from a limited form of mental incompetence is fully bound by those commandments whose rational fulfillment is not affected by his mental condition.