Why are faith and surrender most important in a devotee? Bhagawan reminds us through an episode from the Mahabharata.

One evening Krishna took Arjuna far out of Dwaraka city and while they were alone together, He pointed at a bird flying over their head and asked him: "Arjuna, isn't that a dove?" Arjuna agreed and said that it was indeed a dove. Suddenly, Krishna turned towards him and said, "No, it is a crow." Arjuna concurred and said, "I am sorry, it certainly is a crow." Immediately, Krishna asked him, "A crow? No, it must be a kite. Isn’t it so?" and Arjuna again promptly agreed: "Yes. It is a kite." At this, Krishna smiled and asked Arjuna, "Are you in your senses? What exactly do you see? How can the same bird be a dove, a crow and a kite?" Arjuna said, "Who am I to dispute your statement? You can make it a crow even if it is not one, or change it into a kite. I have found that the safest thing is to agree with You, in full faith. I know of no other course." Only after this test of unflinching faith, Krishna assured Himself of the credentials of Arjuna to receive the holy Gita.