People often quote the Bible. Sometimes different people will quote the Bible to support whatever idea they have decided needs to be bolstered, whether the Bible is really saying that or not. So we might think we don't need to consider its credentials. The Bible tells me so and that's all I want to know. Then we are flumoxed when others don't accept our word from this important book.
Even more dangerously, we might not remember the credentials ourselves. Challenges to the Word sound so reasonable. The Devil knows how to exploit any little doubt. How can you really know. All this seems a little far fetched, unscientific, foolish. Human reason gets put above the clear words, because if something doesn't make sense, or if its hard to believe, then why do I need to hold on to that Word. We pick and choose what verses have real authority. In a moment of crisis, in the midst of doubts, when you really need a firm foundation, forgetting the credentials of God's Word is a devasting mistake.
This is my Son, whom I love. Listen to him. That is a strong credential. God the Father has approved of everything Jesus had ever done. He approves of everything Jesus has said and would say. Peter would recall, we are witnesses of his majesty. John would wonder, we have seen his glory. If this glory, this sign were not enough, God proved this for all to see, by raising him from the dead. Here on the mount of transfiguration, again on Calvary and the empty tomb, God gave Jesus the highest credential.