You may have heard the names of Droṇācārya and Ekalavya.
They were both present in this world 5000 years ago, at the time
of Kṛṣṇa’s pastimes here. Ekalavya went to Droṇācārya and told
him, “I accept you as my guru.” Droṇācārya replied, “I knew you
would be coming to me even before you came. I know your heart
and pulse; you are against pure bhaktas, and therefore I will not
teach you archery.” Ekalavya then said, “I have accepted you as
my guru, so I must learn something about archery from you.”
Droṇācārya again refused and said, “I cannot give lessons to you.
If you learn archery, you will become a burden to the world.”
Still determined, Ekalavya went to the forest and made a clay
statue of Droṇācārya. He offered praṇāma to that statue and,
repeatedly taking the footdust of that statue, he began to practice
archery with great faith. Practicing archery while regularly
performing arcanā and offering flowers to Droṇācārya, Ekalavya
became a master. Then, one day, when Droṇācārya went to the
forest and saw Ekalavya, he became astonished to see how he
had learned such a high class of archery. When Ekalavya saw
Droṇācārya, he fell at his lotus feet and told him, “What I have
learned, I have learned from you.” Droṇācārya then told Ekalavya,
“If you have really learned archery from me, then I want some
guru-dakṣiṇā.” Ekalavya said, “Whatever you wish, I am prepared
to give. I am also prepared to give my life if you want that.”
Droṇācārya replied, “I want your right-hand thumb.”
You would not be able to do this if you were asked to do so
by your gurudeva, but Ekalavya did it immediately.
Ekalavya was still able to shoot with his remaining four
fingers, but what was the result? During the Mahābhārata battle
he wanted to fight with Kṛṣṇa and kill Him; therefore, Kṛṣṇa
took His Sudarśana cakra and very easily cut off his head.
In this connection, the śraddhā, or faith, of Ekalavya is
compared to a clay pot. If one places a clay pot in fire, it will crack.
The śraddhā of Ekalavya was like that clay. He was selfish and
wanted to ruin the devotees, and because of this ulterior motive,
his śraddhā in making and worshiping a statue of Droṇācārya was
really not śraddhā at all. Our śraddhā should not be like that of
Ekalavya. Rather, it should be like that of Arjuna.
Always remember this and do not associate with Ekalavya.

―Śrīla Bhaktivedanta Nārāyaṇa Mahārāja