Valmiki Ramayana Ayodhya Kanda Sarga 1 Shloka 17
Original Shlokaनाऽऽश्रेयसि रतो विद्वान्नविरुद्धकथारुचिः। उत्तरोत्तरयुक्तौ च वक्ता वाचस्पतिर्यथा।।2.1.17।।
1 source checked for this shloka
अश्रेयसि pursuits not conducive to one's welfare, रतः न not interested, विद्वान् learned, विरुद्धकथारुचिः न not interested in speaking against others, उत्तरोत्तरयुक्तौ in debates, वाचस्पति: यथा like Brihaspati, वक्ता an orator
A learned man, he evinced no interest in pursuits that did not contribute to one's welfare or had he any liking for speaking against others. But in debates his oratorical flourish was comparable to Brihaspati's.