118. ellA pramANangaLilum thEhaththAlE pERenkiRathu; thirumanthraththil AthmAvAlE pERenkiRathu; caramaSlOkaththil IsvaranAlE pERenkiRathu; dhvyaththilE periya pirAttiyArAlE pERenkiRathu.
The sastras other than the Rahasyatraya are focused on the body and therefore state that the goal is achieved through the means of practice and rituals. The Thirumantra is focused on the nature of the soul and therefore states that the goal is achieved through the knowledge of this nature. The Carama Shloka is focused on the independence of the Lord and therefore states that the goal is achieved through Him. The Dvaya mantra (which will be explained henceforth) is focused on Sri Mahalakshmi and therefore states that the goal is achieved through Her.
Sri PBA Swami's Sarartha Deepikai:
What is the special thing that is said in Dvaya mantra? It would be good to see what is said in the Sastras, the Thirumantra and the Carama shloka before seeing what is said in the Dvaya mantra.
All sastras look at the speciality of the chetana. Because the sastras speak of the varNAshrama dharmas and the rituals meant to be followed by chetanas, and these dharmas and rituals are associated with the body that performs them, it can be said that the sastras are focused on the body. Therefore, what is gathered from the sastras is that the chetana gains his goal through the body.
The Thirumantra is focused on the pure soul of the chetana. It speaks of the common nature of all souls and is not tied to the specific body or its varNAshrama dharma. In this Thirumantra it is shown that only when the soul gives up the thought that it can save itself that the protection from the Supreme is realized. Therefore, it can be said that the goal is gained through the knowledge of the soul.
The Carama shloka is focused on the independence of the Lord. Here the Lord says that He will ignore the sins of the chetanas and that He will Himself take the chetana unto His divine feet. Therefore, it is said that the goal is gained through Him.
The Dvaya mantra is focused on Sri Mahalakshmi. Therefore, it says that the goal is gained through Her.
To reach the goal, one needs the body, the soul, Him as well as Her. In this the most important requirement is Her and therefore the Dvaya mantra which states that the goal is achieved through Her is considered as especially great.