Valmiki Ramayana Ayodhya Kanda Sarga 103 Shloka 6
Original Shlokaजघन्यमपि ते पुत्रः कृतवान् न तु गर्हितः। भ्रातुर्यदर्थरहितं सर्वं तद् गर्हितंं गुणैः।।2.103.6।।
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ते पुत्रः your son, जघन्यम् servile task, अपि although, कृतवान् has done, गर्हितः तु is indeed contemptible, न not, यत् the service, भ्रातुः to brother, अर्थसहितम् for the benefit of, तत् सर्वम् all that, गुणैः with virtues, विहितम् is endowed with.
Your son, though engaged in servile tasks (like bringing water), is not to be held contemptible because all the services intended for the benefit of his brother are prompted by virtue.