The idea of faith is central to the response that we need to make to the sacrifice of Jesus. Faith, however, is a more complicated idea than many suppose.
"For I am not ashamed of the gospel, for it is the power of God for salvation to everyone who believes, to the Jew first and also to the Greek. For in it the righteousness of God is revealed from faith for faith, as it is written, 'The righteous shall live by faith.'” (Romans 1:16,17)
The idea of faith certainly includes the idea of believing the truth revealed by God. But having only an academic knowledge of the Gospel, while useful as a guide to life, is not enough to bring salvation. The picture is developed in Romans:
"He will render to each one according to his works: to those who by patience in well-doing seek for glory and honour and immortality, he will give eternal life; but for those who are self-seeking and do not obey the truth, but obey unrighteousness, there will be wrath and fury." (Romans 2:68)
This passage describes judgement according to works. Works are the things that we do, the way that we live our lives and the interactions we have with other people. In this passage it is pointed out that these are what we are judged on. Initially this appears to be a discrepancy in the teaching of the Bible, but in reality the idea of faith is wide enough to fit into both passages. The clue to what is going on is the phrase “obey the truth”. One cannot obey truth unless one knows what it is, but just knowing is not enough. To "obey the truth" one must act on it. This is why we read about patience in well-doing in verse 7.
The connection between faith and action can be seen from examples in the letter to the Hebrews. This passage begins with a statement about faith.
"but my righteous one shall live by faith, and if he shrinks back, my soul has no pleasure in him." (Hebrews 10:38)
The passage starts with the idea that one lives by faith; faith is what makes the righteous live. The passage goes on to make a second statement:
"And without faith it is impossible to please him, for whoever would draw near to God must believe that he exists and that he rewards those who seek him." (Hebrews 11:6)
This describes two points about faith; faith requires belief, at least in the existence of God, and requires action, in that we must then seek God. Thought and action are both parts of faith.
The passage then goes on to provide a list of examples of faith. These are taken from the Old Testament and include accounts of Noah, Abraham, Jacob, Moses and the like. Here is part of the account of Abraham:
"By faith Abraham obeyed when he was called to go out to a place that he was to receive as an inheritance. And he went out, not knowing where he was going. By faith he went to live in the land of promise, as in a foreign land, living in tents with Isaac and Jacob, heirs with him of the same promise." (Hebrews 11:8,9)
This tells us one of the things that Abraham did by faith. He left his family and his city and went out to be a nomad, not initially knowing where he was going to. He did this because he believed the promises that God made to him.
A second incident from the life of Abraham is also described in Hebrews 11:
"By faith Abraham, when he was tested, offered up Isaac, and he who had received the promises was in the act of offering up his only son, of whom it was said, 'Through Isaac shall your offspring be named.'” (Hebrews 11:17,18)
This is the incident where Abraham was commanded to offer Isaac as a sacrifice. Abraham believed God and trusted that he would somehow protect his son, so he started the process of sacrifice. God did deliver Isaac from death, and Abraham had showed his faith.
The important thing here is that Abraham showed his faith by the things that he did. His faith was not merely a theory. It was something that informed his life and drove him on to action. Abraham’s faith included action, and it was because of this action that he was acceptable to God.
This picture is confirmed by a parallel account in the letter of James.
"Was not Abraham our father justified by works when he offered up his son Isaac on the altar?" (James 2:21)
This passage clearly identifies Abraham as being justified by what he did, identified by the word “works”. One might ask what is going on here, and the answer is simple. Faith includes action. Thus Abraham’s faith was of value because it affected the way that he lived his life. Had he only believed what God had said, and not done anything, then he would not really have had faith.
The point is picked up in the next verse in the letter:
"You see that faith was active along with his works, and faith was completed by his works;" (James 2:22)
The point is that Abraham’s faith was shown by his works - by what he did.
This explanation is repeated many times in James chapter 2:
v17 So also faith by itself, if it does not have works, is dead.
v20 Do you want to be shown, you foolish person, that faith apart from works is useless?
v26 For as the body apart from the spirit is dead, so also faith apart from works is dead.
The point is that for faith to be real it must affect our actions. The clearest statement of this principle is this:
"But someone will say, 'You have faith and I have works.' Show me your faith apart from your works, and I will show you my faith by my works." (James 2:18)
The consequence of this is that what we believe in our heads is not enough to be faith. Neither is what we feel in our hearts. Both of these are pointless without what we do with our hands. To be faithful we not only need to believe God, but need to live a life where we act on that belief.