What is scriptural source of the verse whose translation is " Your head can be given, ..but the Shodashi Vidya of the Devi can not be given"?

Question

There is a famous saying associated with Sri Vidya which goes like this:

"Your head can be given, your soul can be given but the Shodashi Vidya of the Devi can not be given"

Here reference is to a powerful and secret mantra of Mother Goddess.

Recently, i have found the original sloka, translation of which is the above saying.

AsyA MahAtyamtulam Jihvakotisatairapi | Vaktum Na Sakyate Devi Kim Punah Panchabhinarmukhaih || Api Priyatamam Deyam SutadAradhanAdhikam | Rajyam Deyam Siro Deyam Na Deyo ShodhashAkshari ||

...........

[Lord Shiva says to Devi] Its unmatched greatness can not be described even if someone has hundred crores of tongues. How can my five faces describe its greatness then? The most loved objects of someone, son, wife, wealth, kingdom and even one's head can be given, but shodakshari can't be given

By studying the verses that are found along with these verses, i am guessing that the verses are from one of the Yamala Texts (like Rudra Yamala, Brahma Yamala, Vishnu Yamala etc). Or it can be present in some other Agamas as well.

Question- Which Agama is the source of the verses in question?

Answer 1

The second half of this sloka is the tenth sloka of the Lalitatrishati stotra, in the Lalitopakhyana part of the Brahmanda Purana. This occurs before the actual stotra, when Sri Hayagriva meditates upon Lalitambika and Kameshvara so that he can impart the Trishati to Agastya who has been waiting for three years in the same position. In regard to what is to be imparted, the quoted sloka was given as a command from Devi Lalitambika to Hayagriva.

Sri Devi Uvacha:

Ashvananaavayoh Pritih Shaastra Vishvaasine Tvayi|
Rajyam Deyam Shiro Deyam Na Deyaa Shodashakshari ||10||

"Oh Hayagriva, we (Kameshvara and myself) are pleased with you, the repository of Scripture. A Kingdom can be given, your head can be given, but the Shodashakshari mantra is not to be given."

So. there is a scriptural source for the actual injunction, but I am not sure of the source of the dialogue between the divine couple.

Answer 2

The closest verse I could find is the last verse of the Samayachara Tantra, quoted on page 43 of this book:

Rajyam deyam siro deyam na deyam tantram adbhutam
shadamnayeshu kathitam tantram paramadurlabham.
Yad idante vararohe maya sarva (sic) prakasitam
yatha (sic) gopyam ca subhage matrijarapadam yatha.
Iti (sic) Srisamayacaryatantre (sic) Haragaurisamvade caturdasu-
patalah.

But what it says is that one should rather give up one's kingdom and head than give up "this wonderful Tantra", not the Shodashakshari mantra. But considering that the Samayachara Tantra is part of the Sri Vidya tradition, it likely contains the Shodakashari mantra, so this admonition would apply to that too.