(By 2001:4898:80e8:2:6178:1502:98bd:59cc)

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There is no evidence that the Sanskrit chorus in the song is from Ramayana's Sundar Kand. The reference given merely provides translation and mentions nothing about hanuman or Ramayana. I also checked the Sanskrit version of Valmiki version and the verses are nowhere to be found in Sundar Kand or even in Kishkinda Kand.