Pentecost Sunday Feast: 7 weeks after the Firstfruit Feast.
Pentecost means 50th, so the 50th day after the Feast of Firstfruits; for the Jews at the time the Feast Day celebrating that God gave the 10 Commandments from Heaven to Moses.
For Christians, that Pentecost Sunday, 7 weeks after the Firstfruits Sunday in the Feast of Unleavened Bread, is also the day that God's Spirit was poured out, as can be read in resp. Acts 2:1-4 and Acts 2:38:
"When the day of Pentecost came, they were all together. Suddenly there came a sound from heaven as if a mighty wind came up, and it filled all the house where they were sitting. Then they saw something that sounded like tongues of fire. it seemed, and it divided and descended upon each of them, and they were all filled with the Holy Spirit, and began to speak with tongues, as the Spirit gave them to speak."
"Start a new life," answered Peter, and be baptized, every one of you, in the name of Jesus Christ, to receive the remission of your sins; and you shall receive the Gift of the Holy Spirit."
During that day of the Outpouring of God's Spirit, the baptism that is unto Christ alone (Galatians 3:27, Acts 19:5) but also led to the reception of God's Spirit, which is logical. However: from after the Outpouring period: after the baptism to Christ, prayer with the laying on of hands is needed to join God who is a Spirit (John 4:24) and also takes place in order to receive God's Spirit anchored and the Spiritual Gifts as can be read in resp. Acts 19:6 and Acts 8:17-18:
"Paul laid his hands on them, and the Holy Spirit came upon them. They spoke in strange tongues and prophesied."
"Then Peter and John laid their hands on them, and they received the Holy Spirit. When Simon saw that through the laying on of the apostles' hands the Spirit was given...".
Although the Outpouring has already taken place and 7 Spirits have been poured out over the Earth, this Feast of Weeks (Deuteronomy 16:9-10) is also a permanent Feast of God. (And God is 1, Romans 3:30). So Christians also celebrate this Feast.
You can read more about reuniting with God through His Spirit through with the laying on of hands here: Reuniting with God who is a Spirit
You can read more about the Feasts of God here: God's Feasts & Agenda