The prophet named first in Peter’s sermon was Joel. The verse began in Joel 2:28 And it shall come to pass afterward, that I will pour out my spirit upon all flesh; and your sons and your daughters shall prophesy, your old men shall dream dreams, your young men shall see visions: 29 And also upon the servants and upon the handmaids in those days will I pour out my spirit.

Source:

Acts 2:16-18