Valmiki Ramayana Sundara Kanda Sarga 51 Shloka 21
Original Shlokaतत् त्रिकालहितं वाक्यं धर्म्यमर्थानुबन्धि च। मन्यस्व नरदेवाय जानकी प्रतिदीयताम्।।5.51.21।।
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तत् that, त्रिकालहितम् good for all three times, past present and future, धर्म्यम् is righteous, अर्थानुबन्धि च and provide you material wealth, वाक्यम् these words, मन्यस्व think, नरदेवाय to the lord of the people, जानकी Janaki, प्रतिदीयताम् return.
"Think that my advice is beneficial to you for you present, past and future. It is righteous. It will provide you material wealth too. Hence return Sita to the lord of the people.