Valmiki Ramayana Sundara Kanda Sarga 26 Shloka 6
Original Shlokaअश्मसारमिदं नूनमथवाप्यजरामरम्। हृदयं मम येनेदं न दुःखेनावशीर्यते।।5.26.6।।
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अथवा or, मम my, इदम् this, हृदयम् heart, नूनम् surely, अश्मसारम् made of stone, अजरामरमपि with no age or death, येन since, दुःखेन grieving, नावशीर्यते it does not riven
"It may be, that my heart is made of stone or it has no age or death since it does not riven even with grief.