गोविन्द भाष्य (श्रील बलदेव विद्याभूषण - अचिन्त्यभेदाभेद वेदान्त ब्रह्मसूत्र भाष्य सटीक)

aśuddham—impure; iti—thus; cet—if; na—not; śabdāt—because of Śruti-
śāstra.
If it is said to be impure, then I reply: No, for that is the statement of the Śruti-
śāstra.
Purport by Śrīla Baladeva Vidyābhūṣaṇa
Here someone may object: It is not at all logical to say that the scriptures'
statement that the descending soul, accompanied by the remnant of his karma,
takes birth in the body of a rice plant or similar species, is only a metaphor, and
the soul does not really take birth in those species for the soul has no remaining
karma to push it into that birth. The so-called pious deeds performed to attain
residence in Svargaloka are actually impure. This is because the Agniṣomīya-yajña
and other yajñas like them involve violence to animals. The scriptures give the
following prohibition:
mā hiṁsyāt sarva-bhūtāni
"Never commit violence to anyone."*
Therefore, by performing these yajñas there is a pious portion, which sends the
performer to Svargaloka, and also an impious portion, which forces him to take
birth as a rice plant or similar species. In the Manu-saṁhitā (12.9) it is said:
śarīra-jair karma-doṣair
yāti sthāvaratāṁ naraḥ
"A person who sins with his body becomes an unmoving plant."
Therefore the statement that the descending soul takes birth as a rice plant or
similar being should be taken literally.
If this is said, then the sūtra replies: "na" (No. It is not so). Why not? The sūtra
explains: "śabdāt" (Because that is the statement of the Śruti-śāstra). The Vedas
order:
agnīṣomīyaṁ paśum ālabheta