Valmiki Ramayana Ayodhya Kanda Sarga 42 Shloka 1
Original Shlokaयावत्तु निर्यतस्तस्य रजोरूपमदृश्यत। नैवेक्ष्वाकुवरस्तावत्सञ्जहारात्मचक्षुषी।।2.42.1।।
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तस्य that Rama, निर्यतः as he was going, रजोरूपम् the form of dust, यावत् as long as, अदृश्यत was visible, तावत् so long, इक्ष्वाकुवरः the best of Ikshvaku dynasty, king Dasaratha, आत्मचक्षुषी his eyes, नैव सञ्जहार did not withdraw.
As long as the dust raised by the wheels of the chariot of Rama (who was departing to the forest) was visible, Dasaratha, the best of the Ikshvakus, could not withdraw his eyes (from Rama). Grief stricken Dasaratha falls down-- denounces Kaikeyi--reaches the chamber of Kausalya.