Chuck Swindoll offers this wonderful introduction to James 2:14-26 in his commentary on James:

Many years ago I was driving through our town with a couple of my young kids in the backseat. As children do, they were singing a song they had learned in Sunday school. Now, this was long before they made kids in the backseat wear seatbelts, so one was laying on the seat, the other on the floor. That kind of thing today makes us cringe, but many of you are old enough to remember when that was typical. I couldn’t see them back there, but I could sure hear them belting out that song at the top of their little voices: “If you’re saved and you know it, say ‘Amen!’” And they’d shout, “Amen!”

Eventually they wrangled me into singing along. As we got to the last verse where we’re supposed to “do all three,” I stopped at a red light. With the window rolled down, I was shouting, “If you’re saved and you know it, do all three!” And I stomped, shouted “Amen,” and clapped my hands. Just then I realized we were being watched by two sophisticated-looking people in the car beside us. Well, I should say I was being watched—because they couldn’t see the two kids singing with me, lying down on the back seat!

I could tell by the looks on their faces, they were shocked. They must have thought I was nuts, intoxicated, high, or worse—but they weren’t going to stick around to find out. Their car took off as soon as the light turned green. I wanted to chase them down and explain, “There are two kids in the back seat that got me into this!” But I shrugged my shoulders and thought, “Who cares?”

Then, as I accelerated through the green light, we were at the part of the song where we sang, “If you’re saved and you know it, then your life will surely show it.” And I stopped singing. They kept on, but I stopped. Immediate conviction set in. I thought, “Lord, does my life really show it?” I sure showed something to those people in the next car over, but I was only a little embarrassed about that minor social infraction. What about all the things I’m called to do daily as a believer in Christ—all those things that cut crosswise against cultural norms and society’s expectations? So I began to quickly review the past weeks, months, and years, trying to determine if my life really showed my faith. That simple children’s song got to me.

Someone once said that faith is like calories: you can’t see them, but you can always see their results! That’s the major theme resonating throughout James’s letter. We can boil it down to one word—results. Real faith results in genuine works. And nowhere does James more passionately argue and illustrate this theme than in 2:14-26. This passage forces us to answer that penetrating question, “If you say you believe like you should, why do you behave like you shouldn’t?”

Insights On James, 1 & 2 Peter: 13 (Swindoll’s Living Insights New Testament Commentary, Charles Swindoll