अत एकहल्मध्येऽनादेशादेर्लिटि

ए is substituted for the short अ standing between two simple consonants of a verbal अङ्ग (stem), before the personal endings of the लिट् (Perfect Tense) which have an indicatory क् -- असंयोगाल्लिट् कित् 1.2.5, provided that, at the beginning of the root, in the reduplication, no other consonant has been substituted and when this ए is substituted, the reduplicate is elided.
Thus रेणतुः, रेणुः, येमतुः, येमुः, पेचतुः, पेचुः, देभतुः, देभुः ॥ Why 'for अ'? Observe दिदिवतुः, दिदिवुः the इ is not replaced. Why do we say 'short अ'? Observe ररासे, ररासाते, ररासिरे ॥ Why do we say 'standing between two simple consonants'? Observe ररक्षतुः, ररक्षुः ॥ Some say this example is not appropriate, for by 1.2.5, the Perfect affixes are not कित् here, as they come after a conjunct consonant. The following is then more appropriate :-तत्सरतुः and तत्सरुः ॥ Why do we say 'which has no substituted consonant in the reduplicate'? Observe चकणतुः, चकणुः, जगणतुः, जगणुः, बभणतुः, बभणुः ॥

The substitution referred to here must be caused by the affixes of the Perfect, therefore, the rule will apply to नेमतुः, नेमुः, सेहे and सेहाते, सेहिरे though णम् and षह् are the roots, and ण् and ष् are changed to न and स ॥ The substitution of जश् consonant or a चर् consonant in the reduplicate, should not be here considered asiddha (8.4.54, read with 8.2.1). That substitution will be considered a substitution for the purposes of this sutra and will make the stem आदेशादिः, as is indicated by the special exception made in favor of फल् and भज् 6.4.122. If the form of the letter is not changed in the reduplicate, by substitution, then such substitution will not make the stem आदेशादिः ॥ Thus by 8.4.54, a चर् letter (च, ट, त, क, प, श, ष, स) is substituted for a consonant (other than a nasal and a semi-vowel) in the reduplicate.

Thus in पच् the reduplicate is पपच्, the first प is also a substitute, for the चर् substitute of प will be प ॥ Such substitutes, however, are not meant here.
This we learn from the implication (jnapaka) of sutra 6.4.126 where exception is made in case of शस् and दद् ॥ Therefore, where the substitute is a different letter, then the reduplicate becomes adesadi: otherwise not.

When the affixes are not कित् or ङित् the rule does not apply: as अहं पपच, अहं पपठ ॥

Vart:- ए is substituted for the अ of दम्भ under similar circumstances :-thus देभतुः, देभुः ॥ The elision of the nasal by 6.4.24, would be considered asiddha by 6.4.22, hence this vartika.

Vart:- ए is substituted for the अ of नश and मन before affixes other than those of लिट् ॥ As अनेशम्, मेनका ॥ अनेशम् is the Aorist in अङ् of नश् which belongs to Pushadi roots 3.1.55. मेनका is formed by वुन् 3.1.150. Padamanjari gives अनेशन् (3rd Plural), and quotes अनेशन्नस्येषवः ॥

Vart:- In the Vedas, ए is substituted for the अ of अम् and पच् before affixes other than those of the Perfect, as व्येमानम्, (वि + अम् + चानश्, the augment मुक् being dropped); पेचिरन् instead of पचेरन्, the Imperfect of पच् ॥ The shortening is also a Vedic irregularity.

Vart:- So also of यज् and वप, as आयेजे and आवेपे the Imperfect Vedic forms. The augment आट् being added by 6.4.73.