This advice was given by Maricha to Ravana, while suggesting him not to kidnap Mata Sita, this is mentioned in Ramayana – Aranya Kanda, chapter 37 verse 2
Sanskrit Shloka
सुलभाः पुरुषा राजन्सततं प्रियवादिनः।
अप्रियस्य तु पथ्यस्य वक्ता श्रोता च दुर्लभः।।3.37.2।।’
Hindi Meaning
हे राजन, प्रिय बोलने वाले पुरुष तो सुलभता से मिल जाते हैं, परंतु अप्रिय एवम् हितकर बात कहने वाले और सुनने वाले लोग बड़े दुर्लभ होते हैं !
English Meaning
O king, it is always easy to find men who speak pleasing words, but it is difficult to get speaker and listener who use words unpleasant but beneficial.
