Valmiki Ramayana Aranya Kanda Sarga 43 Shloka 27
Original Shlokaपश्यास्य जृम्भमाणस्य दीप्तामग्निशिखोपमाम्। जिह्वां मुखान्निस्सरन्तीं मेघादिव शतह्रदाम्।।3.43.27।।
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जृम्भमाणस्य while it is yawning, अस्य its, मुखात् from the mouth, निस्सरन्तीम् stretching, दीप्ताम् glowing, अग्निशिखोपमाम् like flaming fires, मेघात् from the cloud, शतह्रदाम् इव like the lightning, जिह्वाम् tongue, पश्य see.
Look at his tongue stretched out of the mouth while yawning. It is glowing like flaming fire. It is like the lightning sparkling in the cloud.