SriKantha Shivacharya in his commentary on Brahma Sutra 3.2.38 gives various quotes to prove it is Parameswara alone who is actually worshipped in all sacrifices. The full Bhasya is as:

And because so He is declared to be- (III - ii 38 )

Indeed the Parames'vara is declared to be the lord of all works,—as worshipped by their means and as the dispenser of their fruits,—in the following passages :

"...Rudra, the Lord of hymns, the Lord of sacrifices, possessed of medicaments that confer delight. " Secure Rudra, the king of sacrifice.. "

The Smriti, too, based on these passages of the S'ruti, declares that the Parameswara is the lord of all sacrifices :

" Let everyone worship, by soma, the Divine Being who is associated with Uma and who is adorned with the moon."

And the Ramayana, too, says:;

" There is no sacrifice, higher than the horse-sacrifice (as'vamedha), in the matter of Rudra's worship."

And in the Chamakam also (Taittiriya-Samhita IV vii. I—11)—which read "May food (come) to me), may permission (come) to me ; may Dhatri (come) to me, .may VishnU (come) to me '—all things such as food, and all Gods such as Vishnu are declared as things to be given, so that,—as the sole alternative left,—the Parames'vara alone is the dispenser of the fruits of all actions. Therefore it is the Parames'vara alone who is to be worshipped by all sacrifices, and who is the dispenser of all fruits.

Most of the quotes above are traceable to various scripture. For instance the first quote is from RigVeda 1.43.4. The second quote 'Rudra, King of Sacrifices' is from Yajurveda 1.3.14.

But where does Ramayana state that quote of Ashwamedha sacrifice being worship of Rudra?. Is that quote from Valmiki Ramayana or from some other Ramayana ?