Faith in the context of the OT rests on a foundation that the person or object of trust, belief, or confidence is reliable. Trust in Yahweh is expressed through loyalty and obedience. The theme of responsive obedience is emphasized in the Torah (Exod. 19:5). In the later history of Israel, faithfulness to the law became the predominant expression of faith (Dan. 1:8; 6:10). OT faith, then, is a moral response rather than abstract intellect or emotion.
Faith is a central theological concept in the NT. In relational terms, faith is foremost personalized as the locus of trust and belief in the person of Jesus Christ.
In the Gospels, Jesus is spoken of not as the subject of faith (as believing in God), but as the object of faith. In the Synoptic Gospels, faith is seen most often in connection with the ministry of Jesus. Miracles, in particular healings, are presented as taking place in response to the faith of the one in need of healing or the requester. In the Gospel of John, faith (belief) is presented as something that God requires of his people (6:28
29).
In the book of Acts, “faith/belief” is used to refer to Jews and Gentiles converting to following the life and teachings of Jesus Christ and becoming part of the Christian community. The book correlates faith in Christ closely with repentance (Acts 11:21; 19:18; 20:21; 26:18).
Paul relates faith to righteousness and justification (Rom. 3:22; 5:11; Gal. 3:6). In Ephesians faith is shown as instrumental in salvation: “For it is by grace you have been saved, through faith—and this not from yourselves, it is the gift of God” (2:8).
In Hebrews, faith is described as “being sure of what we hope for and certain of what we do not see” (11:1). Faith thus is viewed as something that can be accomplished in the life of the believer—a calling of God not yet tangible or seen. To possess faith is to be loyal to God and to the gospel of Jesus Christ despite all obstacles. In the Letter of James, genuine works naturally accompany genuine faith. Works, however, are expressed in doing the will of God. The will of God means, for example, caring for the poor (James 2:15–16).
In 1 Peter, Christ is depicted as the broker of faith in God (1:21), whereas in 2 Peter and Jude faith is presented as received from God (2 Pet. 1:1). In the Letters of John “to believe” is used as a litmus test for those who possess eternal life: “You who believe in the name of the Son of God, . . . you have eternal life” (1 John 5:13).