Brahma Sutras – According to Shankara 3-3-27
Topic 27 - Upāsanās mentioned in connection with certain sacrifices are not parts of them and hence are not inseparably connected with them
तन्निर्धारणानियमः, तद्दृष्टेः, पृथग्ध्यप्रतिबन्धः फलम् ॥ ४२ ॥
tannirdhāraṇāniyamaḥ, taddṛṣṭeḥ, pṛthagdhyapratibandhaḥ phalam || 42 ||
tat-nirdhāraṇa-aniyamaḥ—No rule about the inviolability of that; tat-dṛṣṭeḥ—that being seen (from the Śruti); pṛthak—separate; hi—for; apratibandhaḥ—non-obstruction; phalam—result.
42. There is no rule about the inviolability of that (i.e. Upāsanās connected with certain sacrifices); that is seen (from the Śruti itself); for a separate effect (belongs to the Upāsanās), i.e. non-obstruction (of the results of the sacrifice).
The question whether certain Upāsanās mentioned with some sacrifices are part of those sacrifices and therefore inseparably connected with them, is taken up for discussion.
This Sutra says that such Upāsanās do not form a part of the sacrifice, for there is no rule as to their inseparability.
On the other hand the scripture clearly says that the sacrifice can be performed with or without them: “Therefore both he who knows this, and he who does not, perform the sacrifice” (Chh.1.1.10). See also Chh.1.10.9.
The Śruti, moreover, mentions a separate effect of the Upāsanās apart from that of the sacrifice, i.e. the non-obstruction (i.e. enhancement) of the results of the sacrifice:
“The sacrifice which a man performs with knowledge etc. is more powerful” (Chh. 1. 1. 10).
It means that the original sacrifice would have got its own results, but the Upāsanā enhances those results. So the results of the sacrifice with or without the Upāsanā are different.
Therefore the Upāsanā does not form part of the sacrifice, and hence may or may not be performed according to the pleasure of the sacrificer.
Non-obstruction may be explained thus: The sacrifice without the Upāsanā would have had the prescribed results, but the Upāsanā prevents any obstruction to those results. This, however, does not make it a part of the sacrifice.
Sometimes the results of the sacrifice are delayed owing to the intervention of any bad Karma of the sacrificer, but the Upāsanā destroys the effect of that, and the results are attained earlier.
Here, however, the sacrifice does not depend upon the Upāsanā for its results, though they might have been delayed. Hence the Upāsanā is not a part of the sacrifice, and is therefore optional.