yasyobhayaṁ sādhu sa śikṣakāṇāṁ dhuri pratiṣṭhāpayitavya eva ||
Somebody has the learning (knowledge or expertize) in contained in himself fine. (but not capable of transferring it to others). Some other has specialized skill of transferring (teaching the knowledge whatever he has got)(but he need not have accumulated knowledge like the other). One who has got both of them (the qualifications - skill in learning himself and in teaching others), is to be placed first among the teachers. (He is the first rate Teacher).
The gist is that though everybody can learn and teach others, some have the capacity of learning a lot of things, but lack the skill of teaching it to others and some others have the skill of teaching (whatever they have learnt), but lack the skill of learning (i.e.accumulation of knowledge).
This is common experience in the field of teaching. Those who have great knowledge, need not be the good teachers and the best teachers need not be having great knowledge (but enough to teach what the student needs).
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