Rom 12:3; For through the grace given to me I say to everyone among you not to think more highly of himself than he ought to think; but to think so as to have sound judgment, as God has allotted to each a measure of faith.
Everyone has at least a measure of faith, even if they say they don't.
Over 40 times the phrase "your faith" is used. It's usually what causes something to happen in the New testament.
Matt 9:22; But Jesus turning and seeing her said, "Daughter, take courage; your faith has made you well." At once the woman was made well.
Matt 9:29; Then He touched their eyes, saying, "It shall be done to you according to your faith."
Matt 15:28; Then Jesus said to her, "O woman, your faith is great; it shall be done for you as you wish." And her daughter was healed at once.
Mark 5:34; And He said to her, "Daughter, your faith has made you well; go in peace and be healed of your affliction."
Mark 10:52; And Jesus said to him, "Go; your faith has made you well." Immediately he regained his sight and began following Him on the road.
Luke 7:50; And He said to the woman, "Your faith has saved you; go in peace."
Luke 8:25; And He said to them, "Where is your faith?" They were fearful and amazed, saying to one another, "Who then is this, that He commands even the winds and the water, and they obey Him?"
Luke 8:48; And He said to her, "Daughter, your faith has made you well; go in peace."
Luke 17:19; And He said to him, "Stand up and go; your faith has made you well."
Luke 18:42; And Jesus said to him, "Receive your sight; your faith has made you well."
Luke 22:32; but I have prayed for you, that your faith may not fail; and you, when once you have turned again, strengthen your brothers."
Mark 7:28; But she answered and *said to Him, "Yes, Lord, but even the dogs under the table feed on the children's crumbs."
Mark 7:29; And He said to her, "Because of this answer go; the demon has gone out of your daughter."
.. or not happen, as the case may be.
Matt 17:19; Then the disciples came to Jesus privately and said, "Why could we not drive it out?"
Matt 17:20; And He *said to them, "Because of the littleness of your faith; for truly I say to you, if you have faith the size of a mustard seed, you will say to this mountain, 'Move from here to there,' and it will move; and nothing will be impossible to you.
Matt 13:58; And He did not do many miracles there because of their unbelief.
Sometimes a lack of faith is what prevents something from happening.
1Thes 3:10; as we night and day keep praying most earnestly that we may see your face, and may complete what is lacking in your faith?