Students fall under three distinct categories.
A student of the first category tends to be arrogant and egoistic. He goes to a teacher more to display his own knowledge than to learn from him!
The second category student tries to test the teacher’s knowledge. He merely analyses and criticizes the teacher. He too does not tend to learn.
The third category alone comprises the perfect, ideal student. He approaches a teacher with sincerity and devotion. The sole purpose of his association is to learn and gain knowledge. Krishna places Arjuna in that category.
Great masters have imparted knowledge to the world from time immemorial. They do so for the benefit of the people. These divine souls harbour no other motive. Krishna recognizes Arjuna’s devotion and delight to learn. This inspires Krishna to impart the sacred knowledge. Herein, Krishna follows this great tradition while imparting knowledge to Arjuna.
Source: Excerpts from the commentary on “Srimad Bhgavat Gita”for the verse 1 of Chapter X by A.Parthasarathy.