Valmiki Ramayana Ayodhya Kanda Sarga 118 Shloka 5
Original Shlokaयां वृत्तिं वर्तते रामः कौसल्यायां महाबलः। तामेव नृपनारीणामन्यासामपि वर्तते।।2.118.5।।
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महाबलः mighty, रामः Rama, कौसल्यायाम् in Kausalya, यां वृत्तिम् such treatment, वर्तते behaves, अन्यासाम् with others, नृपनारीणामपि consorts of the king, तामेव the same way, वर्तते behaves.
Mighty Rama shows the same behaviour and treatment towards the other consorts of the king as he does towards his own mother Kausalya.