Sutra:
3. Thirumanthraththinudaiya seermaikkup pOrumpadi prEmaththOdE pENi anusanthikka vENum.

Meaning:
This Thirumanthram has to be recited by giving it the respect due while keeping it hidden from those who are not qualified for it.

Sri PBA Swami's Sarartha Deepikai:
The greatness of the Thirumanthra is beginning to be explained from this point on. The first is the correct method of reciting it and keeping it in one's heart. The meanings of the four Vedas (Rk, Yajur, Sama and Atharvana) are contained within this manthra. It is considered as the best amongst manthras, the best amongst rahasyas, and the best amongst the best things. As such, a person holding it in his heart should keep it there and recite it daily with the respect that is due to it, with a melted heart while with-holding it from those who are not qualified to hold it in their hearts. This also means that it should not be recited when the heart is not prepared and it should also not be recited in a loud voice.