How do we know the doctrine of salvation by faith is true?

The doctrine of salvation by faith is firmly grounded in biblical revelation, as both the Old and New Testaments affirm this truth. In the narrative of the brass serpent, the act of looking at the serpent represents the faith required for healing, illustrating that salvation and deliverance come from God alone. Similarly, in the New Testament, Jesus explicitly connects this event to His crucifixion, stating that just as the serpent was lifted up, so He must be lifted up to bring eternal life to those who believe (John 3:14-15). This consistent biblical theme underscores that salvation is not based on our works or merits but is received through faith in Christ, confirming the doctrine for all who trust in Him.