Sutra:
168. idhilE thirumanthraththil sonna prApyaththai visathamAga anusandhikkiRadhu.

Meaning:
The service described in the Thirumantra is explained clearly (that is, Mahalakshmi is a joint recepient of the chetana's service), in this (latter) part of the Dvaya mantra.

Sri PBA Swami's Sarartha Deepikai:
In the Thirumantra, it is said "nArAyaNAya", meaning that the chetana asks to perform service at the lotus feet of Narayana. There it neither says openly that Narayana is the one with whom Sri Mahalakshmi is present eternally nor does it say that the chetana's gin is nothing but the service. Those are distinctly said here and therefore it can be taken that the latter part of the Dvaya mantra details the latter part of the Thirumantra.