Sutra:
7. Sakala sAsthrankaLAlum piRakkum gnyAnam SvayamArjitham pOlE; thirumanthraththAl piRakkum gnyAnam paithrukathanam pOlE.

Meaning:
The knowledge gained by a person through Sastras such as Srutis and Smritis are like the wealth gained by him after much effort whereas the knowledge gained by a person through the Thirumanthra upadesam by an acharya is easily obtained like wealth inherited from his forefathers.

Sri PBA Swami's Sarartha Deepikai:
A question might arise that, are there not several Sastras that He Himself has provided to this world? Why should a person not study these works and gather the knowledge held within? Are they not a way to reach Him; why would one have to try to reach Him through the recitation of the Thirumanthram? The fact that the knowledge gained from Thirumanthram is better than that gained from Sastras is shown here through the use of an example. A person works hard and gathers wealth; another gains wealth without any effort by inheriting it from his forefathers. While both enjoy the wealth, since one person struggled to obtain his wealth it is tinged with some pain; whereas the other person got his wealth easily and therefore enjoys it more. Similarly the wealth of knowledge obtained through Thirumanthram by the grace of an acharya will be most pleasing.