Acts 2
19I will show wonders in heaven above
And signs in the earth beneath:
Blood and fire and vapor of smoke.
20 The sun shall be turned into darkness,
And the moon into blood,
Before the coming of the great and awesome day of the Lord.
21 And it shall come to pass
That whoever calls on the name of the Lord
Shall be saved.’

From my commentary:
It would be many years until the gospel was offered to Gentiles, yet Peter’s sermon text announced the gospel invitation by saying, whoever calls on the name of the LORD shall be saved.

Peter’s first sermon under the power of the Holy Spirit was to call on the name of the Lord and you shall be saved.