Old Testament Faith
The faith of the O.T. fathers is repeatedly used in the N.T. as our example, and for exhortation (Heb. 11). Abrahams faith was counted unto him for righteousness (Rom. 4:3), and we are told this was written for our sake (v.23-24). The just shall live by faith is from Hab. 2:4. So, study what Girdlestone (Synonyms of the Old Testament) says about the use of the word faith in the Old Testament.
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The general Hebrew word for truth or truthfulness, and faith or faithfulness, is a derivative of the verb Aman, whence the word Amen draws its origin. Aman in its simple active form signifies to nurse or nourish up; in the passive, to be firm and establish, and hence steadfast; and in the Hiphil or causative form, to take as established, and hence to regard as true, to realize, or to believe. The last is its most general rendering.
The form Emunah, generally rendered faithfulness, is found in Hab. 2:4, where we read, The just shall live by his faith — words which ought to be read in connection with the fifth verse of the first chapter, I will work a work in your days which ye will not believe, though it be told you.
The most general word, however, to express trust is bathach, to confide in, or lean upon. Here it is to be remarked that, though we are in the habit of speaking of faith and trust as the same thing, the Hebrew has two distinct words for them, and so has the LXX. Whilst aman answers to pisteuo, to believe or realize; bathach, to trust, is never so rendered.... The man who believes God is he who, having received a revelation from Him, realizes it, and acts it as true. (emph. mine, rt) The man who trusts God is he who casts all his hopes for the present and future on God. It is the former quality, not the latter, that God regards as a condition of justification. Faith must precede hope, because a hope for the future which is not grounded upon a present acceptance with God is no hope; and a sense of acceptance which is not accompanied with a living, working faith is an unreality.
We now approach the N.T. with a clear distinction between faith on the one hand, and trust and hope on the other. Faith is the taking God at His word, while trust and patience and also hope are the proper fruits of faith, manifesting in various forms the confidence which the believer feels. A message comes to me from the Author of my existence; it may be a threat, a promise, or a command. If I take it as yea and amen, that is Faith; and the act which results is an act of ainunah or faithfulness towards God. Faith, according to Scripture, seems to imply a word, message, or revelation.
So the learned Romaine says in his Life of Faith; — Faith signifies the believing the truth of the Word of God; it relates to some word spoken or to some promise made by Him, and it expresses the belief which a person who hears it has of its being true; he assents to it, relies upon it, and acts accordingly; this is faith. (From pages 102-105.)