If you preach grace—that God saves you through simple faith in Jesus for eternal life, apart from your works (cf. Gal 2:16)—then why do good? 

What’s the point of all the love commands in the NT (e.g., “serve one another in love,” Gal 5:13), if your eternal destiny in heaven or hell is not on the line? 

People who are heavily invested in legalistic religion struggle with that question. Their whole religious and moral life is oriented towards becoming good enough to be saved. That’s their main motivation for doing good. So when you tell them no one is good enough to be saved, that the only condition to be born again is to believe, you delegitimize their entire perception of how they relate to God and man. 

And they ask the question—why do good? What’s the motivation? 

The Bible gives us two powerful models of persons who do good without trying to earn their salvation by it. 

First, think about God. 

God is good and does good to you. But what is His motivation? Is it so He can be saved from hell? Of course not. God doesn’t need salvation—He is salvation. So why does He do good? Because He loves you. He knows you need His help, so He helps because He wants what is good for you. Grace is His reason. 

Second, think about Jesus. 

Jesus loves you and serves you. But why? What’s His motivation? Is it because He is trying to earn His salvation? Again, the answer is no. Jesus is the source of eternal life—He doesn’t need to earn it. So why does He love? Because He does! Love is its own explanation, isn’t it? 

Love finds value in the beloved for their own sake. But unconditional love creates value in the beloved, whether they are loveable or not. We’re so used to conditional “love” that depends on the other person meeting our expectations. We’re not used to God’s unconditional “one-way love.” That is, we’re not used to grace. We’re not used to people showing grace to us or showing grace to others. 

Why love? Why do good to others if it is not to avoid hell? God and Jesus give us the model: because of grace.