A biblical understanding of how God’s promises relate to repentance will not only prevent us from presuming on God’s promises apart from a turning to him, but also guard us from taking credit for any of our repentance. Accordingly, Acts 3:19-21 will answer a couple of prevalent questions that can often arise throughout our Christian lives: In light of our weakness and failings, can we count on God to be true to his promises? If we think the answer is ‘no,’ we will perpetually be floating between self-righteous performance and self-atoning penance.
Here’s another prevalent question: Should we expect to receive God’s grace if we refuse to turn from sin to Christ? If we say ‘yes,’ we fall into the same trap of blindness that characterized the Jews of the 1st century: “We’re physical descendants of Abraham, so we’re in as God’s chosen people.” That’s similar to saying: “We’re Bible believing Christians; we sit under expository preaching and embrace reformed doctrine.” But consider this: Can those things atone for our sin or sanctify us apart from faith?
So just to summarize: We must neither trust in our own performance for the security of our salvation, nor can we presume on God’s grace. Our sin does not cancel out God’s promises, but, rightly understood, that truth must not excuse or promote sin. In fact, the Apostle Paul writes in Rom. 2:4 Or do you think lightly of the riches of His kindness and tolerance and patience, not knowing that the kindness of God leads you to repentance?
So amidst a strong call for these Jews who previously disowned Jesus to repent in Acts 3, Peter reiterates several key promises that are expressions of God’s immeasurable faithfulness and kindness. This is how Christ’s preeminence is promoted in that Christ purchases God’s promises, even for those who desired to kill him, and part of that purchase is the gift of repentance. So if we are comprehending this passage how we should, then God’s faithfulness and grace should be revealed in stunning ways. In other words, we should see ourselves as more undeserving of salvation and thus saved strictly due to the character of our God.