The id of idam is elided before a vibhakti affix beginning with a consonant.,
As आभ्याम्, एभिः, (VII. I. 11) एभ्यः एषाम्, एषु ॥ For म् is substituted अ by 7.2.102, and for अ + अ = अ by (VI. I. 97). The rule: (I. I. 52) by which a substitute replaces only the final letter, does not apply here, on the maxim मानर्थके अलोऽन्त्यविधिः ॥ For no purpose is served by eliding merely the final म् of इदम् ॥ Hence इद् is elided. Or it may be said that the sutra does not teach the elision of इद्, but of अन् which was substituted for इद् by the preceding sutra.,