While there are many things we may learn from Peter’s sermon on Pentecost (Acts 2:14-41), let’s consider today how he implicitly teaches that Jesus is God. He did not declare it as bluntly as we often do today, perhaps because directly calling any man ‘God’ would repulse his listeners before they would listen to reason. So he did it indirectly.
Now the record in Acts 2 is also very useful to show that the concept that Jesus is God was believed by the disciples soon after the Resurrection. The doctrine of Jesus Christ’s divinity was not made up by John, and most certainly was not made up after the 3rd century AD (as some non-Christians say). And the first time the disciples publicly professed it was probably as early as Pentecost.
What happened during Pentecost was a truly epic miracle – the Holy Spirit descended upon the disciples of Jesus Christ and they spoke in languages which they had never learnt. And it seemed that in the crowd of listeners, the Holy Spirit also caused many to hear whatever was preached in their first language. This gift of tongues was given for the purpose of evangelism – such that people might hear, comprehend, and believe the gospel.
The people were astonished, of course. Never in biblical history had God given people the power to overcome the legacy of Babel. Then Peter stood up and explained that such a sign given through the Holy Spirit was foretold,
[Acts 2:16-21] But this is what was uttered through the prophet Joel:
“‘And in the last days it shall be, God declares, that I will pour out my Spirit on all flesh, and your sons and your daughters shall prophesy, and your young men shall see visions, and your old men shall dream dreams; even on my male servants and female servants in those days I will pour out my Spirit, and they shall prophesy.
And I will show wonders in the heavens above and signs on the earth below, blood, and fire, and vapour of smoke; the sun shall be turned to darkness and the moon to blood, before the day of the Lord comes, the great and magnificent day.
And it shall come to pass that everyone who calls upon the name of the Lord shall be saved.’
Let’s look at the last line of the quote above. The name of the Lord, what is it? In Greek, the word is Kurios. It is a title often used to address one who is supreme in authority, or one held to be master. In the New Testament, it is often used for God. But for the rest of Peter’s sermon, he does not again talk about calling upon ‘the Lord’ to be saved. Instead, Peter talks about how the miracles, the Scriptures, and the resurrection prove that Jesus is both Lord and Christ. The listeners realised to their distress that the long-awaited Christ had been murdered, and that as part of the community which brought about his public execution, they bore this sin too.
These listeners were ‘devout men’ (Acts 2:5). We may be sure that they feared God, and probably recognised that the risen Christ now had every right to bring judgement upon them. Perhaps many also perceived that Peter and the apostles were speaking as prophets, and wanted to heed their warning. Thus pricked in their hearts, they asked for a solution. Only then did Peter tell them what was necessary for their sins to be forgiven,
[Acts 2:38,39] And Peter said to them, “Repent and be baptized every one of you in the name of Jesus Christ for the forgiveness of your sins, and you will receive the gift of the Holy Spirit. For the promise is for you and for your children and for all who are far off, everyone whom the Lord our God calls to himself.”
Do you see the connection between the highlighted portions? In verse 21, “everyone who calls upon the name of the Lord shall be saved,” and then in verse 38 “repent and be baptized every one of you in the name of Jesus Christ.” Peter seems to imply that the name of the Lord is in fact Jesus Christ! He did not say ‘repent and be baptised in the name of the Lord’, though he could have. By teaching people to trust in the name of Jesus Christ, Peter draws such a link that made Jesus equal with the Lord whom people need to call upon.
Peter quotes most of Joel 2:28-32 at the start of his sermon, except the last sentence. Then at the conclusion of his sermon (Acts 2:39), he returns to this same passage to boldly declare the sovereignty of God in salvation. The connection is there. And the extent to which Peter upheld the divinity of Jesus is clearer when we examine carefully the reference from the prophet Joel.
[Joel 2:28-32] “And it shall come to pass afterward, that I will pour out my Spirit on all flesh; your sons and your daughters shall prophesy, your old men shall dream dreams, and your young men shall see visions. Even on the male and female servants in those days I will pour out my Spirit.
“And I will show wonders in the heavens and on the earth, blood and fire and columns of smoke. The sun shall be turned to darkness, and the moon to blood, before the great and awesome day of the LORD comes.
And it shall come to pass that everyone who calls on the name of the LORD shall be saved. For in Mount Zion and in Jerusalem there shall be those who escape, as the LORD has said, and among the survivors shall be those whom the LORD calls.
The Hebrew word for ‘LORD’ which Joel used is Yahweh (sometimes pronounced as Jehovah), which we recognise as a name that the Israelites only used for the one true God. In all likelihood, some of the devout men who heard Peter would have known the Hebrew text of Joel, and realised the implication that Jesus was none other than God come in the flesh. Not all the people accepted the teaching of the apostles that day, but 3000 believed and were baptised. If they were baptised into the name of the Father, the Son, and the Holy Spirit (according to Matthew 28:19), that would also have been an opportunity to explain who these persons are.
And so, Peter’s sermon uses a substitution of names to show that Jesus is indeed the eternal God who saves. I have used these passages in Acts 2 and Joel 2 while conversing with Jehovah’s Witnesses and with friends who may have met them. Perhaps, we might also learn from Peter’s example when witnessing to Muslims or atheists who deny that Jesus is God. Peter wove the doctrine of Jesus’ deity into his message, emphasising the magnitude of their offence first. After all, when a person realises how great his need for a Saviour is, he will be ready to admit that such a Saviour would have to be God himself.
 Incidentally, Acts 1:8 shows how even the name of Jehovah’s Witnesses is incorrect – Jesus sent his disciples saying, “you will be my witnesses”. So the true church witnesses to Jesus Christ, the Son of God.