There are lots of "faith formulas" out there. It seems like people debate this way of looking at faith vs. that, and others are digging for some hidden secret or understanding that will "unlock" faith for them from the Bible, or trying to find someone to physically impart "faith" to them through the laying on of hands, or some other silly thing. But the Bible is really simple: "Faith is being sure of what you hope for, certain of what you do not see." (Heb 11:1, NIV'78) Literally, Heb 11:1 says
εστιν δε πιστις ελπιζομενων υποστασις πραγματων ελεγχος ου βλεπομενων"pistis" (faith/belief) "estin" ("is" or "is being"):
estin de pistis elpizomenon upostasis pragmatwn elegchos ou blepomenon
There is one word (not two), the Greek word πιστος ("pistos"), and its various inflections, πιστ__ "pist__," that can be translated interchangeably "faith" or "belief" (if a noun), or "have faith" or "believe" (if a verb).
So to begin with, I'm sure you've heard people say that there is a "difference" between "faith" and "belief." That is technically not true from a scriptural point of view, since there is only one word.
That said, the English word "faith" has a stronger connotation than "belief." What people who say "there is a difference between 'faith' and 'belief'" really mean, and rightly so, is that there is a difference between putting your trust in something and mere intellectual acknowledgment about the fact that the thing they "believe" is true, which would just be a matter of "knowing" or "knowledge."
"Knowledge/understanding" in the New Testament would be the Greek noun γνωσις ("gnosis") or the corresponding verb γινωσκω ("ginosko"), which means "know." Now γνωσις is a sure and absolute knowledge or understanding about something. So that's what people often mean in English when they say "I believe that..."
On the other hand "faith" in English, and according to the various English definitions as usages, is far more loaded with various religious connotations.
So that should summarize the Greek vs. English span of word interpretations.
What you need to do is "just believe" (Mark 5:36, Luke 8:50)
You can see how action is tied into this, not by definition, but by consequence: You haven't seen it yet, but you are convinced it will happen and expect it to happen. So, if you are "convinced," if you "expect it to happen," then you will speak and act accordingly.
Obviously, scriptures make clear that "faith" is a decision and conviction that will naturally result in corresponding actions, if it is true that you really "believe" it, as James in particular elaborates on at length. (Also compare Romans 4, being justified in the sight of God, our Creator, by "faith alone," vs. James 2, being justified in the sight of all creation by "'faith'+works"). So you can find out what a person "believes" by what they do and other things they say.
So again, "faith" and "belief" are the same word in the scriptures. Since what you believe results in corresponding actions, it will become apparent what you "believe" by what you do. Obviously, "doing" isn't a part of "believing" and doesn't cause "believing." That would be "works" or "performance," whereas it is "faith" ("believing") that pleases God (Heb 11). That said, "believing" does cause "doing" if you really "believe."
Then there's "unbelief." Well, that's just απιστος ("a-pistos"), so you just add the prefix α ("a"), the negative particle meaning "without/apart" to it, which works just like in English. So it's the same Greek word in the negative.
For "little faith" (as in "you of little faith") Jesus actually either used "a-pistos" (lack of faith), or ολιγοπιστος ("oligo-pistos"), which literally means "few-faith" or "few-believing," which would be awkward to translate literally. But "few" is a measure of quantity, not magnitude; qualitatively "sparse." So a person with ολιγοπιστος has faith for (or believes) few things. There isn't actually "little faith" or "big faith."
Then there's that English translated word "doubt," which is from one of two or three Greek words (see What is "doubt" according to the scriptures?. But all of the "doubt" verses are just tied into lack of faith, some kind of thinking that contradicts what you are supposed to be believing in. So really, the point is to "just believe."
Then you hear people point out about the Word of God "nullified" by the traditions of men (Matt 15:6, Mark 7:13), which word is ακυροω ("a-kuroO" which means to invalidate (i.e. to consider "without" "validity") the Word of God. But that's just back to unbelief as well, if you hold traditions above the Word of God. So don't believe traditions, just believe the Word of God!
So, you see, we are back to "just believe." All the words, "believe," "faith," "unbelief," "doubt," and "nullifying traditions of men" boil down to whether or not you just "believe."
This stuff is very, very simple.
Some other "faith formulas" I've heard:
This actually comes from a quote from the father of the demon-possessed boy that the disciples couldn't heal: "I am believing; help my unbelief." (Mark 9:24). This is a statement coming out of the mouth of a desperate and distraught father of an afflicted child, not Jesus. The father's words are not authoritative. They don't even have to make sense. They are just a record of what he said. All he was focused on was getting his son healed. First he was asking the disciples to do it, then when they couldn't, he brought the boy to Jesus. He said to Jesus, "But if you can do anything, take pity on us and help us." Does this sound like a statement of faith? Jesus rebukes him, saying, "If you can? Everything is possible for him who believes." To which the father of the boy responds, literally, "I-am-believing master be-you-helping of-me to-the un-belief." Then Jesus, not the father, kicked the demon out of the boy. Later the disciples asked Jesus why they couldn't do it, and Jesus said "Because of your unbelief." (Matt 17:20). So we are back to "just believe."
The principle behind "faith" is very simple. "Faith is being sure of what you hope for, certain of what you do not see" (Heb 11:1). People try to make it complicated, or religious, or dig and search for some "hidden secret" that will unlock the key to understanding faith, when there is no such secret or hidden meaning. It is just right there in plain view, in terms that a child can understand. "Just believe." And keep believing.
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