Valmiki Ramayana Aranya Kanda Sarga 29 Shloka 20
Original Shlokaसर्वथैव लघुत्वं ते कत्थनेन विदर्शितम्। सुवर्णप्रतिरूपेण तप्तेनेव कुशाग्निना।।3.29.20।।
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कत्थनेन by boasting, तप्तेन heated, सुवर्णप्रतिरूपेण looking like gold, कुशाग्निना इव by the fire of kusa grass, सर्वथैव by all means, ते your, लघुत्वम् meanness, विदर्शितम् is exhibited.
All your meanness is exhibited by your boasting just as the kusa grass caught by fire appears like gold.