Valmiki Ramayana Yuddha Kanda Sarga 124 Shloka 7
Original Shlokaएतत्पश्ययथाक्षिप्रंप्रतिगच्छामतांपुरीम् । अयोध्यांगच्छतोह्येषपन्थाःपरमदुर्गमः ।।6.124.7।।
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तांपुरीम् that city, यथा as, प्रतिगच्छाम to return, एतत् these, पश्य see, अयोध्याम् Ayodhya, गच्छतः depart, एषःपन्थाः this path, परमदुर्गमःहि very difficult also
" As it is very difficult to return to that city, think of the path to depart."