BRS 2.4.260

Bhāvasya pavanopamā would normally mean that the bhāva is compared to the wind. Pavana in the compound word would be resolved into the locative: pavane upamā, meaning “bhāva is similar to the wind.” However, in verse 262 there is the phrase bhāvasya dīpenebhena vopamā. Here the words dīpena and ibhena are in the instrumental case rather than the locative case. Thus to keep uniformity, it should be understood that pavana in the compound pavanopamā should similarly be taken in the instrumental case. This is the intention of the author. By the context, the instrumental in the compound however cannot be considered to mean “with” as in “he went with his son.” However, use of instrumental with upamā is forbidden by Pāniṇi. Tulyārthair atulopamābhyāṁ tṛtīyā ’nyatarasyām: the instrumental case or genitive case is used with words meaning “like” or resembling” but not with the words upamā or tulya (equal or same); the genitive case only is used with them. (Pāṇini 2.3.71). But then again in the commentary on the sūtras, counter examples of these two words when they mean “similar” are given. Examples of the use of these words (genitive case) are as follows: upamā strī-mukhasyenduḥ (a comparison of the moon with the face of a woman) and candrasya strī-mukham tula (the woman’s face is like the moon). Thus, according to Pāniṇi’s rule, the instrumental case is not supposed to be used with either tula or upamā when they mean “similar.” However, the instrumental case can indicate the locative case, as in the phrase kāṁsya pātryā bhuṅkte: he eats with a bell-metal plate (pātryā is in the instrumental case), though the meaning is the same as “he eats on a bell-metal plate (locative case).” This then is the meaning of the phrase bhāvasya dīpenebhena vopamā in the instrumental. By the rule kartṛ-karaṇe ca krṭā bahulam (Pāṇini 2.1.32) the instrumental case then forms a compound. The same usage should be understood in the following verses.