Which Hindu scripture is the mantra "Sri Ram Jai Ram Jai Jai Ram" from?

Question

I have tried this mantra only 108 times and it definitely helps in third eye activation. But I cannot find which scripture it is from?

श्री राम, जय राम, जय जय राम

Answer 1

I think I've found it in Ram Rahasya Upanishad:

Reciting the name Sri Rama and Jayarama thereafter, the wise one says jaya jaya twice, Rama who sheds joy on the mind (56)

Jai Shri Ram!

Answer 2

It is said in Ram Rahasya Upanishad as well as Anand Ramayan Manohar khand sarg-7 said by shri Krishna himself:-

मंत्रा नानाविधाः सन्ति शतशो राघवस्य च। तेभ्यस्त्वेकं वदाम्यद्य तव मंत्रं युधिष्ठिर।।४४ श्रीशब्धमाद्य जयशब्दमध्यं जयद्वेयेनापि पुनः प्रयुक्तम्। त्रिःसप्तकृत्वो रघुनाथनामजपो निहन्याद्द्विजकोटिहत्याः।।४५

There are many mantras related to bhagwan shri Ram that you can write, chant. If chanting use Tulsi mala but chant should be in 1 lakh or 1 crore. At first shri Ram, in middle use jai Ram and in end, jai jai Ram ( श्री राम जय राम जय जय राम). This mantra when chanted crore times can get rid of crore times of brahma hatya.