We have many explanations for the harm we cause in life, including not foreseeing the effects of our actions. But though ignorance may explain our sins, does it excuse us from guilt? Peter speaks to this topic. He has accused Jerusalem of unjustly executing Messiah (v14-15). Now he admits that they acted without realising what they were doing (v17). This seems remarkable given Israel was told about their coming king and the suffering he would face (v18). And surely Jesus’ miracles and teaching showed them all they needed to know about him? But it wasn’t so. We human beings have a range of traits which keep us from learning: bias, laziness, cowardice, pride, arrogance and other ways can prevent us from seeing what we ought to see. That’s happened in Jerusalem: Jesus was killed in ignorance. The killing, however, was still sin (v19).
So Peter calls his hearers to wake up to what they’ve done and turn from it. This needs humility, a pushing away of proud self-defence. If they’ll admit their wrong then forgiveness can come. This is still true for us. Too easily we excuse our bad behaviour by pointing to all that influences us. That’s foolish. We must own up to our sins before the Lord. Peter promises the crowd that if they do then mercy will be given. Ignorance may not excuse wickedness, but God does respond to it with patience (Ex 34:6). If the people repent then their sins can be wiped fully away. Instead of reaping disaster, they can find wholeness again (like the lame man, v16) through refreshing times. Then God will send the risen Messiah back (v20). Not that Peter is promising any timescales for this since Jesus prohibited such knowledge (1:6,7). But he can promise that Christ will return and put the world back together as it should be (v21), just as the prophets predicted.
Of course, Peter’s ignorant hearers might still question all these claims. Can a Messiah who died on a cross really do anything? Can he even be Messiah? But Peter insistently presses the point over and again that God is in all of this. He predicted it, he brought it about and he will complete it. God can do what we cannot do; he has power over death itself! God brings hope, as Peter points out from the Old Testament. Moses (v22) told Israel that God would raise up a new prophet like him (Dt 18:15,18) and when he came they needed to listen to him, because to ignore the word of God is to risk losing everything (v23). And Moses wasn’t alone in pointing forward with hope if Israel would listen to the Lord: Samuel brought the same hope (eg 1Sa 12:20-25) especially in his anointing of David (2:30; 1Sa 16:1); other prophets spoke in similar fashion (v24). Indeed this promise drives all the way back to Abraham, the forefather of Israel who received a covenant from God which promised rich blessing (v25; Ge 12:1-3; 15:18). This comes true in Jesus who rose from the dead, sits at God’s right hand and has poured out the Holy Spirit on his people (2:31-33). However, Peter also presses the crowd to respond to this before they lose their opportunity, for God will soon move on to go worldwide with this blessing (v26).
That’s now happened: Israel’s words have become words for all the world. God has been patient with our ignorance (17:30), but now Jesus is turning people from their wicked ways all across the earth and granting them times of refreshing, a new wholeness of life. We need to believe this: trusting Jesus, learning from him and looking forward to his return with all it will bring.