Luke 17:5 The apostles said to the Lord, “Increase our faith!”
Hebrews 11:1
(1984 NIV) Faith is being sure of what we hope for and certain of what we do not see.
(Weymouth) Faith is a well grounded assurance of that for which we hope, and a conviction of the reality of the unseen.
(HCSB) Faith is the reality of what is hoped for, the proof of what is not seen.
Faith (pistis - "to believe") is a firm persuasion and belief in the truth. Faith is not just a mental assent but a conviction, a surrender to that truth with actionemanating from and in accord with one's surrender; a steadfast pursuit of righteousness. (1 Timothy 6:11b)
Westminster Larger Catechism, Q. 73
Faith justifieth a sinner in the sight of God, not because of those other graces which doth always accompany it, or of good works that are the fruits of it, not as if the grace of faith, or any act thereof, were imputed to him for his justification; but only as it is an instrument by which he receiveth and applieth Christ and his righteousness.
Tertullian De Carne Christi (c. 203-206)
The Son of God died: it is by all means to be believed, because it is absurd.
And, buried, He rose again: it is certain, because impossible.
(I believe that Christ died for me because it is incredible; I believe that He rose from the dead because it is impossible.)
Augustine
Seek not to understand that you may believe, but believe that you may understand.
John Owen "A Practical Exposition on Psalm 130"
v. 5 - I wait for the LORD, my soul waits, and in his word I put my hope.
See in the meantime that your faith brings forth obedience, and God in due time will cause it to bring forth peace.
Richard Sibbes "Divine Meditations", No. 85
God will try the truth of our faith, so that the world may see that God has such servants as will depend upon His bare word.
John Flavel The Mystery of Providence Opened
Providence so orders the case that faith and prayer need to be exercised to close the gap between our needs and supply. Thus, the goodness of God is more magnified in supplying the provisions we need. Man’s extremity is God's opportunity.
John Bunyan "Christian Behavior" on Titus 3:7-8
Faith receiveth the promise, embraceth it, and comforteth the soul unspeakably with it. Faith is so great an artist in arguing and reasoning with the soul, that it will bring over the hardest heart that it hath to deal with. It will bring to my remembrance at once, both my vileness against God, and his goodness towards me; it will show me, that though I deserve not to breathe in the air, yet that God will have me an heir of glory.
C.H. Spurgeon
Faith is both God's gift and man's act. The Lord is the author of our faith, but we ourselves believe. God gives us faith, but He does not believe for us.
Faith is the soul's eye by which it sees the Lord. Faith is the soul's ear by which we hear what God the Lord will speak. Faith is the spiritual hand which touches and grasps the things not seen as yet.
"A Lecture For Little-Faith"
https://archive.spurgeon.org/sermons/0205.php
R.C. Chapman, 'Choice Sayings', Notes of Expositions of the Scriptures, 1883
God is honored by faith, and most honored when faith discerns His love and truth behind a thick cloud of His ways and providence.
J.C. Ryle Old Paths, "Faith"
Would you have more faith? Do you find believing so pleasant that you would like to believe more? Then take heed that you are diligent in the use of every means of grace, diligent in your private communion with God, diligent in your daily watchfulness over time, temper, and tongue, diligent in your private Bible-reading, diligent in your own private prayers. It is vain to expect spiritual prosperity, when we are careless about these things. Let those who will, call it over-precise and legal to be particular about them. I only reply, that there never was an eminent saint who neglected them.
Would you have more faith? Then seek to become more acquainted with Jesus Christ. Study your blessed Saviour more and more, and strive to know more of the length and breadth and height of His love. Study Him in all His offices, as the Priest, the Physician, the Redeemer, the Advocate, the Friend, the Teacher, the Shepherd of His believing people. Study Him as one who not only died for you, but is also living for you at the right hand of God, as one who not only shed His blood for you, but daily intercedes for you at the right hand of God, as one who is soon coming again for you, and will stand once more on this earth. The miner who is fully persuaded that the rope which draws him up from the pit will not break, is drawn up without anxiety and alarm. The believer who is thoroughly acquainted with the fullness of Jesus Christ, is the believer who travels from grace to glory with the greatest comfort and peace. Then let your daily prayers always contain these words, "Lord, increase my faith" (Luke 17:5).
A.B. Simpson
One of the most essential qualities of faith that is to attempt great things for God and expect great things from God, is holy audacity. Where we are dealing with a supernatural Being, and taking from Him things that are humanly impossible, it is easier to take much than little; it is easier to stand in a place of audacious trust than in a place of cautious, timid clinging to the shore. Likewise, seamen in the life of faith, let us launch out into the deep, and find that all things are possible with God, and all things are possible unto him that believeth.
A.W. Tozer
Faith is confidence in God's self-revelation as found in the Holy Scriptures.
The certainty of the believer may be understood when it is remembered that it springs from his faith in the Scriptures as the full and true revelation of the mind of God to men. His dogmatism has back of it the strong “thus saith the Lord” of prophet and apostle.
The man of faith is so sure of his position before God that he can quietly allow himself to be overlooked, discredited, and deflated, without a tremor of anxiety. He is willing to wait out God's own good time and let the wisdom of the future judgment reveal his true size and worth. The man of unbelief dare not do this. He is so unsure of himself that he demands immediate and visible proof of his success. His deep unbelief must have the support of present judgment. He looks eagerly for evidence to assure him that he is indeed somebody. And of course this hunger for present approval throws him open to the temptation to inflate his work for the sake of appearances.
D.L. Moody
Faith does not look within; it looks without. It is not what I think, nor what I feel, nor what I have done, but it is what Jesus Christ is and has done, and so we should trust in Him who is our strength, and whose strength will never fail.
John Stott
Faith is a reasoning trust, a trust which reckons thoughtfully and confidently upon the trustworthiness of God.
George Mueller
If we desire our faith to be strengthened, we should not shrink from opportunities where our faith may be tried and therefore, through the trial, be strengthened.
CAUTION
A.W. Tozer The Set of the Sail
You have only to imagine your closest personal friend coming to you and stating in cold seriousness that he no longer has any confidence in you. I do not trust you. I have lost confidence in your character. I am forced to suspect every move you make. Such a declaration would instantly alienate friends by destroying the foundation upon which every friendship is built. Until your former friends opinion of you had been reversed there could be no further communion. Only a restored faith could bring about a restored friendship.
People do not go boldly to God and profess that they have no confidence in Him, and no one except the rare professional unbeliever is willing to witness publicly to his low view of God. The frightful thing, however, is that people everywhere act out their unbelief with a consistency that is more convincing than words.
C.H. Spurgeon, “Morning”, March 4 on 2 Corinthians 12:9 “My grace is sufficient for thee.”
https://www.ccel.org/ccel/spurgeon/morneve.d0304am.html
The God who has been sufficient until now should be trusted to the end.
F.B. Meyer Our Daily Walk on Isaiah 38:14
May I trust more than I know, and believe more than I see; and when my heart is overwhelmed within me, lead me to the Rock that is higher than I.
D. Martyn Lloyd-Jones
Studies in the Sermon on the Mount
The trouble with many Christians is that we believe in the Lord Jesus Christ, but we do not believe Him...we do not take the Scripture as it is and believe it and live by and apply it.
The God whom I am trusting for today, I will trust for tomorrow.
Spiritual Depression: It's Causes and Cure, Chapter 10, "Where Is Your Faith"
https://www.monergism.com/where-your-faith
Faith says: "I cannot believe that He who has brought me so far is going to let me down at this point. It is impossible, it would be inconsistent with the character of God." So faith, having refused to be controlled by circumstances, reminds itself of what it believes and what it knows.