"The apostles said to the Lord, 'Increase our faith!'" (Lk 17:5). Jesus had been teaching them and apparently they felt that they didn't have the ability to carry out what had been taught. Jesus said they would need "'faith like a mustard seed'" (:6). One time they couldn't cast a demon out and Jesus said it was "'Because of the littleness of your faith'" (Mt 17:20). Jesus explained "'if you have faith the size of a mustard seed . . . nothing will be impossible to you'" (:20). Previously Jesus had taught that "'The kingdom of heaven is like a mustard seed . . . [which] is smaller than all other seeds; but when it is full grown, it is larger than the garden plants'" (Mt 13:31-32). Therefore your faith must grow "but God was causing the growth" (1Co 3:6). This demonstrates "your faith would not rest on the wisdom of men, but on the power of God" (2:5).
Abraham "grew strong in faith" (Ro 4:20). He was "fully assured that what God had promised, He was able also to perform" (:21). Abraham had confidence in God. Jesus said "'Have faith in God'" (Mk 11:22). "By grace you have been saved through faith" (Eph 2:8). It is by righteousness "which is through faith in Christ, the righteousness which comes from God on the basis of faith" (Php 3:9). It is based upon "the faith of the gospel" (1:27) and "the hope of the gospel" (Col 1:23) in which "you continue in the faith firmly established and steadfast" (:23). Your faith grows as you mature and it is recognizable as when Paul "heard of your faith" (Col 1:4, Eph 1:15). The Colossians had been "built up in Him and established in . . . faith" (2:7). Paul rejoiced to see "the stability of your faith in Christ" (:5). It was Paul's responsibility to be with them "for your progress and joy in the faith" (Php 1:25). He was in the "sacrifice and service of your faith" (2:17). He stated that "your faith grows" (2Co 10:15). Faith grows when you are "striving together for the faith of the gospel" (Php 1:27).