When we read Amos, we see that God judges the nations by their actions toward other human beings, but He judges Israel - His people - by their love for Him.
We've already seen how we get this pretty wrong by the way that we try to hold non-believers accountable to the word of God. But we're getting it just as wrong for ourselves - those of us inside the church. And we're doing this in two weirdly opposite ways.
On one hand, we're tempted to say that if we are simply being judged on whether or not we love God, then we must only confess, perhaps even just once, that we love God and we will be "good." This is how we get the doctrine we preach that says that if you pray a prayer in your heart just one time, with just one breath over the course of your living, that accepts Jesus Christ and confesses Him, then you get to go to heaven. Forever. Just like that. Jesus doesn't require anything more of you than one prayer with one breath of your life.
And, of course, that is not consistent with what the Bible teaches about what it means to become a child of God.
But the other way we're getting it wrong is just as dangerous. We tell ourselves that because we are now Christians, all that matters is how we treat one another. After all, that's what Jesus said, isn't it? That they'll know we are Christians by the way that we love.
So we spend our lives trying to do good deed, to be good persons, to love one another (whatever that means to us), and then we build a theology of our own salvation around how good we are. It's nothing more than the same works-based faith that Jesus died to free us from and the Bible (yes, even the Old Testament) repeatedly warns us against.
We convince ourselves that it's enough, as an act of "worship," to donate to charity, to serve soup in a kitchen, to send a note of kindness, to cook a meal, to...whatever. And we invest our entire life in doing the things that make us look like good persons. That make us look like we care about those around us. And maybe, of course, we do.
In my experience, what happens when we start doing good works, even as an act of loving persons, is that we slowly start to shift our emphasis to those good works. We start to set our eyes on the things of this world and what we can do in it. Slowly, but surely, we lose sight of God entirely, or at least mostly, and settle on the fact that we are going to heaven because we are such thoroughly good persons and how could God not reward us for that?
We become experts at the second-greatest command, thinking it's the first, and we lose sight of what we were actually created for - to be creatures who worship the Creator. To be humans in the image of the God we love first. What is the greatest command? Even the rich man gets this right - it is to love the Lord our God with all our heart, soul, mind, and strength, but we live a faith where too many of us are just trying to avoid the sin not of Israel, but of the Ammonites, so we are too busy being good to one another to give glory to God.
And this is how we end up with a watered-down Gospel where God approves of us on account of our goodness and our love for one another, and in that kind of theology? There's no need for a Cross at all.