How does obedience relate to saving faith?
"What does it profit, my brethren, if someone says he has faith but does not have works? Can faith save him? If a brother or sister is naked and destitute of daily food, and one of you says to them, "Depart in peace, be warmed and filled," but you do not give them the things which are needed for the body, what does it profit? Thus also faith by itself, if it does not have works, is dead. But someone will say, "You have faith, and I have works." Show me your faith without your works, and I will show you my faith by my works. You believe that there is one God. You do well. Even the demons believe--and tremble! But do you want to know, O foolish man, that faith without works is dead? Was not Abraham our father justified by works when he offered Isaac his son on the altar? Do you see that faith was working together with his works, and by works faith was made perfect? And the Scripture was fulfilled which says, "Abraham believed God, and it was accounted to him for righteousness." And he was called the friend of God. You see then that a man is justified by works, and not by faith only. Likewise, was not Rahab the harlot also justified by works when she received the messengers and sent them out another way? For as the body without the spirit is dead, so faith without works is dead also" (James 2:14-26)
According to James faith doesn't truly exist without the evidence of works accompanying the faith. In other words, faith is demonstrated by the things that a person does and not by the things a person claims. The most famous chapter on faith is Hebrews 11 and notice that each example of faith is also an example of work. How do we know that Abel had faith? Because he offered a better sacrifice. How do we know that Enoch had faith? Because he walked with God and did not die. Noah demonstrated his faith by building the ark. Abraham showed his faith by leaving his homeland and by offering up his son Isaac.
Faith and obedient works are inseparable. It is when man tries to pull them apart -- to have one without the other -- that man finds himself in trouble.
Notice the parallels formed between faith and obedience in the following verses:
"And to whom did He swear that they would not enter His rest, but to those who did not obey? So we see that they could not enter in because of unbelief" (Hebrews 3:18-19).
"For indeed the gospel was preached to us as well as to them; but the word which they heard did not profit them, not being mixed with faith in those who heard it" (Hebrews 4:2).
"Since therefore it remains that some must enter it, and those to whom it was first preached did not enter because of disobedience" (Hebrews 4:6).
"Let us therefore be diligent to enter that rest, lest anyone fall according to the same example of disobedience" (Hebrews 4:11).
It should be clear that the writer of Hebrews sees faith and obedience as interchangeable ideas. They are not the same concept, but they are inseparable -- having one implies the other. Paul puts it this way: "But now is manifested, and by the Scriptures of the prophets, according to the commandment of the eternal God, has been made known to all the nations, leading to obedience of faith" (Romans 16:26).
"He who believes in the Son has eternal life; but he who does not obey the Son will not see life, but the wrath of God abides on him" (John 3:36). The Greek word apeitheo that is translated as "does not obey" is very interesting. It means "to disobey, to be unpersuaded, to be disobedient, disloyal, or stubborn." It is properly translated as either disobedient or unbelieving because the ideas are seen as being synonymous.