Om ithyagre vyaahareth nama ithi paschath. Narayanasa ethyuparishath. Om ithyekaksharam. Nama ithi dhwe akshare. Narayanayethi Panchaksharani. Ethadwai Narayanasyashtaksharam padam. Yoha vai Narayanasya ashtaksharam pada madhyethi. AAnapabroova sarva mayurethi. Vindathe Prajapathyam rayasposham gowpathyam thatho amruthathwamasruthe thatho amrutha masnutha ithi. Ethath Sama Veda siro adithe. 3

Tell “Om “ first and then tell “Nama” After this tell “Narayana”. There is one letter in “Om”. There are two letters in “Nama”. There are five letters in “Narayana.” Together is formed the eight lettered “Om Namo Narayana”. He, who tells these eight letters, attains full life without any blemish. He would attain salvation after becoming the lord of the people and be blessed with lots of wealth, lots of cows and all other forms of wealth. Thus is read the Upanishads of Sama Veda.

The above are quoted from the Narayana Upanishad which is linked with the Krishna Yajurveda.

So, it is highly unlikely that the mantra (which is part of a Vedic literature) won't require initiation. Om itself is the first mantra which obviously requires initiation.

Your own question (answered by me) is related here (about whether Om japa is mantra japa or Nama japa): Is chanting “OM” naam japa or mantra japa?

Om ithyagre vyaahareth nama ithi paschath. Narayanasa ethyuparishath. Om ithyekaksharam. Nama ithi dhwe akshare. Narayanayethi Panchaksharani. Ethadwai Narayanasyashtaksharam padam. Yoha vai Narayanasya ashtaksharam pada madhyethi. AAnapabroova sarva mayurethi. Vindathe Prajapathyam rayasposham gowpathyam thatho amruthathwamasruthe thatho amrutha masnutha ithi. Ethath Sama Veda siro adithe. 3

Tell “Om “ first and then tell “Nama” After this tell “Narayana”. There is one letter in “Om”. There are two letters in “Nama”. There are five letters in “Narayana.” Together is formed the eight lettered “Om Namo Narayana”. He, who tells these eight letters, attains full life without any blemish. He would attain salvation after becoming the lord of the people and be blessed with lots of wealth, lots of cows and all other forms of wealth. Thus is read the Upanishads of Sama Veda.

The above are quoted from the Narayana Upanishad which is linked with the Krishna Yajurveda.

So, it is highly unlikely that the mantra (which is part of a Vedic literature) won't require initiation. Om itself is the first mantra which obviously requires initiation.

Your own question (answered by me) is related here (about whether Om japa is mantra japa or Nama japa): Is chanting “OM” naam japa or mantra japa?

Om ithyagre vyaahareth nama ithi paschath. Narayanasa ethyuparishath. Om ithyekaksharam. Nama ithi dhwe akshare. Narayanayethi Panchaksharani. Ethadwai Narayanasyashtaksharam padam. Yoha vai Narayanasya ashtaksharam pada madhyethi. AAnapabroova sarva mayurethi. Vindathe Prajapathyam rayasposham gowpathyam thatho amruthathwamasruthe thatho amrutha masnutha ithi. Ethath Sama Veda siro adithe. 3

Tell “Om “ first and then tell “Nama” After this tell “Narayana”. There is one letter in “Om”. There are two letters in “Nama”. There are five letters in “Narayana.” Together is formed the eight lettered “Om Namo Narayana”. He, who tells these eight letters, attains full life without any blemish. He would attain salvation after becoming the lord of the people and be blessed with lots of wealth, lots of cows and all other forms of wealth. Thus is read the Upanishads of Sama Veda.

The above are quoted from the Narayana Upanishad which is linked with the Krishna Yajurveda.

So, it is highly unlikely that the mantra (which is part of a Vedic literature) won't require initiation. Om is the first mantra which obviously requires initiation.

Om ithyagre vyaahareth nama ithi paschath. Narayanasa ethyuparishath. Om ithyekaksharam. Nama ithi dhwe akshare. Narayanayethi Panchaksharani. Ethadwai Narayanasyashtaksharam padam. Yoha vai Narayanasya ashtaksharam pada madhyethi. AAnapabroova sarva mayurethi. Vindathe Prajapathyam rayasposham gowpathyam thatho amruthathwamasruthe thatho amrutha masnutha ithi. Ethath Sama Veda siro adithe. 3

Tell “Om “ first and then tell “Nama” After this tell “Narayana”. There is one letter in “Om”. There are two letters in “Nama”. There are five letters in “Narayana.” Together is formed the eight lettered “Om Namo Narayana”. He, who tells these eight letters, attains full life without any blemish. He would attain salvation after becoming the lord of the people and be blessed with lots of wealth, lots of cows and all other forms of wealth. Thus is read the Upanishads of Sama Veda.

The above are quoted from the Narayana Upanishad which is linked with the Krishna Yajurveda.

So, it is highly unlikely that the mantra (which is part of a Vedic literature) won't require initiation. Om itself is the first mantra which obviously requires initiation.

Your own question (answered by me) is related here (about whether Om japa is mantra japa or Nama japa): Is chanting “OM” naam japa or mantra japa?