Rom 10:17 So then faith cometh by hearing, and hearing by the word of God.
We have faith in God by hearing the Word of Faith; which is the Word of God.
The Word of God here, is the Word of Faith - the Gospel of Grace; the full gospel.
It is in hearing the faith filled Word of God that faith comes, and it is in hearing the faith filled Word of God that faith is nurtured.
What is preached most times on our pulpits are nothing but sin, condemnation and the wrath of God. Such breeds fear, inferiority, and doubt rather than faith.
It is the hearing of the preached Gospel of the grace and truth of God that came by Jesus Christ, that brings faith.
However, we walk by faith, by first living by faith.
We cannot walk in something we don't have. So we are to live by faith before we walk by faith.
Likewise, We live in the Spirit (i.e having the Spirit of Christ in our hearts - being born again, Rom 8:9) before we can walk in or by the Spirit,
Gal 5:25 If we LIVE IN THE SPIRIT[having the Spirit of God dwell in us by reason of the new birth-being born again], let us also WALK IN THE SPIRIT.
So we live in, before we walk in.
Same is true with faith.
We have to live by faith(i.e having first the faith that came into our hearts when we heard the Gospel of our salvation and received it by that same faith, thus becoming born again) before we can walk by faith.
Rom 1:16 For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation TO EVERY ONE THAT BELIEVETH; to the Jew first, and also to the Greek.
Rom 1:17 For therein is the righteousness of God revealed from faith to faith: as it is written, The just shall live by faith.
So by hearing the Gospel of Christ that saves, we receive faith to believe for salvation, thus receiving Christ and becoming saved.
So in hearing the gospel of salvation, the faith of Christ was imparted unto us to believe and receive the message.
That is, we use His faith(imparted, on hearing the message; Rom 10:17) to believe the faith message,
Rom 10:9 That if thou shalt confess with thy mouth the Lord Jesus, and SHALT BELIEVE IN THINE HEART that God hath raised him from the dead, THOU SHALT BE SAVED.
The faith to believe in the heart comes by hearing the Word of faith- the Word of God.
So the just shall live by faith that came through the preached Gospel (i.e saved and imparted with Eternal life by faith), and then should walk by that faith from then on,
Col 2:6 As ye have therefore RECEIVED CHRIST JESUS THE LORD [by faith that came through the hearing of the Gospel of Chrsit, which is the Word of faith] , SO WALK YE IN HIM[by faith]:
You should know as a believer in Christ that you already have faith in God, if not so, then you were never saved, you are not born again.
So as a born again saint of God in Christ, don't let any one tell you that you don't have faith in God, cause you do, if not you won't have been saved.
As a believer you should learn how to walk by faith, not how to have faith or live by faith; you already have and are living by it; except the term "live by faith" is conveying the thought, "walking or living the day to day life by faith"
You've already got faith, you only need to know how to use it to appropriate all that has been made available for you in Christ.
It is expedient you know how to walk by faith else you will live a defeated life as a Child of God.
You see, we can only enforce to seeing the manifestation of all that belongs to us in Christ through faith.
Eph 1:3 Blessed be the God and Father of our Lord Jesus Christ, who hath blessed us with all spiritual blessings in heavenly places in Christ:
We can only walk in the fullness of these blessings only by standing and holding fast to them by faith.
We will only see the fruit or manifestations of redemption, righteousness, sanctification, wisdom, salvation, and all the other spiritual blessings by standing and walking by faith.
You can only enforce Colossians 1:13 by faith,
Col 1:13 Who hath delivered us from the power of darkness, and hath translated us into the kingdom of his dear Son:
A Christian praying, for ending hours, that the power or authority of witches, wizards and demons should be broken in his or her life is not walking by faith in the light of Colossians 1:13. He is trying to break what only exists in the figment of his imagination, sponsored by the devil; mental strongholds.
And we have been instructed as Christians to cast down these strongholds in 2Corinthians 10:3-5.