Where is the mention of 'Chanting Rama three times is equal to chanting 1000 names of Vishnu'?

Question

In the ending part of Vishnu Sahasranaam Stotra these verses are recited:

पार्वत्युवाच :
केनोपायेन लघुनां विष्णुर्नामसहस्रकम् ।
पठ्यते पंण्डितैर नित्यं श्रोतुमिच्छाम्यहं प्रभो ॥ 26 ॥

pArvatyuvAcha:
keno pAyena lagunA vishNor nAma sahasrakam | paTyate paNDitair nityam shrotumicchAmyaham prabho ||

Parvati said "O lord what is the short method to recite Vishnu Sahasranaam (if I am not able). What is to be chanted for it?"

ईश्वर उवाच
श्रीराम राम रामेती रमे रामे मनोरमे ।
सहस्रनाम तत्तुल्यं रामनाम वरानने ॥ 27 ॥

ishwara uvAcha:
sri rAma rAma rAmethi rame rAme manorame | sahasranAma thatthulyam rAma nAma varAnane |

Ishwara said " O beautiful one!, Chant Rama Rama Rama which rejoices the mind. It is equal to thousand name of Vishnu"

The above verses aren't found in Mahabharata where Bhishma recites Vishnu Sahasranaam. From where are these verses taken ?

Answer 1

These verses are found in Uttar Khanda of Padma Purana in chapter 71. These verses are the last two verses of that chapter.

Parvati Said:
330. if I am unable to recite every day these thousand names of Visnu, then tell me, O bull-bannered god, that name, by which I shall get that fruit (obtained by the recital of Visnu's thousand names).

Mahadeva said:
331. O you beautiful one, O you charming one, (recite) 'Rama, Rama, Rama'. The thousand names are equal to that.
[Chapter 71 Vishnu's One Thousand Names]