In Joel 2:28, what does God promise to pour out on all people?

Answer: His Spirit

"I will pour out My Spirit on all people." Peter quoted this prophecy on the day of Pentecost in Acts 2:17.

“And afterward, I will pour out My Spirit on all people. Your sons and daughters will prophesy, your old men will dream dreams, your young men will see visions. Even on My menservants and maidservants, I will pour out My Spirit in those days.”— Joel 2:28-29 (BSB)