Valmiki Ramayana Kishkindha Kanda Sarga 29 Shloka 14
Original Shlokaयस्तु कालव्यतीतेषु मित्रकार्येषु वर्तते4.29.14।। स कृत्वा महतोऽप्यर्थान्न मित्रार्थेन युज्यते।
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यः he who, कालव्यतीतेषु exceedng the time limit, मित्रकार्येषु in his friend's task, वर्तते acts, सः he, महतः great, अर्थान् effort, कृत्वा does, मित्रार्थेन for the cause of friend, न युज्यते not succeed.
'He who exceeds the time limit in accomplishing a friend's task, and puts forth great effort later succeeds not.