229. The first consonant

The first consonant of a group—whether interior, or initial after a vowel of a preceding word—is by the grammarians either allowed or required to be doubled.

a. This duplication is allowed by Pāṇini and required by the Prātiçākhyas—in both, with mention of authorities who deny it altogether. For certain exceptions, see the Prātiçākhyas; the meaning of the whole matter is too obscure to justify the giving of details here.