This story is when the five Pandavas used to study in the ashram of Guru
Dronacharya. One day Guru Dronacharya taught them to always tell the truth
and never tell a lie and, said to remember this throughout their life. He
also told them to memorize a certain lesson. The next day the Guru made
them stand and turn by turn, memorizing the lesson. All the students
memorized the lesson. When it was Yudhister's turn he said, "Guru, I could
not learn the lesson". The Guru punished Yudhister and taught the others
another lesson. For twenty days Yudhister said the same thing. On the
twenty-first day, the Guru said angrily, "Oh Yudhister, you are a fool.
Could you not learn the small lesson till now". Yudhister said, "Guru,
when you taught to always tell the truth and never tell a lie, I always
tell the truth. But, I could not make my words fully true till now. How
can I say that I have learnt lesson? Only repeating the line is not
learning the lesson, but to follow it, is true study". Then, Guru
Dronacharya said, "Oh my son Yudhister, you are a very clever student".