No one should be allowed to sit on the vyasasana who is not spotless in character and who is not freed from the above-mentioned vices
SB Canto 1
The sages said: Respected Sūta Gosvāmī, you are completely free from all vice. You are well versed in all the scriptures famous for religious life, and in the Purāṇas and the histories as well, for you have gone through them under proper guidance and have also explained them.
A gosvāmī, or the bona fide representative of Śrī Vyāsadeva, must be free from all kinds of vices. The four major vices are (1) illicit connection with women, (2) animal slaughter, (3) intoxication, (4) speculative gambling of all sorts. A gosvāmī must be free from all these vices before he can dare sit on the vyāsāsana. No one should be allowed to sit on the vyāsāsana who is not spotless in character and who is not freed from the above-mentioned vices. He not only should be freed from all such vices, but must also be well versed in all revealed scriptures or in the Vedas. The Purāṇas are also parts of the Vedas. And histories like the Mahābhārata or Rāmāyaṇa are also parts of the Vedas. The ācārya or the gosvāmī must be well acquainted with all these literatures. To hear and explain them is more important than reading them. One can assimilate the knowledge of the revealed scriptures only by hearing and explaining. Hearing is called śravaṇa, and explaining is called kīrtana. The two processes of śravaṇa and kīrtana are of primary importance to progressive spiritual life. Only one who has properly grasped the transcendental knowledge from the right source by submissive hearing can properly explain the subject.