The First Pentecost:

Exodus 32:25-28

When Moses saw that the people were running wild (for Aaron had let them run wild, to the derision of their enemies), then Moses stood in the gate of the camp, and said, “Who is on the Lord’s side? Come to me!” And all the sons of Levi gathered around him. He said to them, “Thus says the Lord, the God of Israel, ‘Put your sword on your side, each of you! Go back and forth from gate to gate throughout the camp, and each of you kill your brother, your friend, and your neighbor.’” The sons of Levi did as Moses commanded, and about three thousand of the people fell on that day."

The Greater Pentecost (Acts 2:36-41):

"Therefore let the entire house of Israel know with certainty that God has made him both Lord and Messiah, this Jesus whom you crucified.”

Now when they heard this, they were cut to the heart and said to Peter and to the other apostles, “Brothers, what should we do?” Peter said to them, “Repent, and be baptized every one of you in the name of Jesus Christ so that your sins may be forgiven; and you will receive the gift of the Holy Spirit. For the promise is for you, for your children, and for all who are far away, everyone whom the Lord our God calls to him.” And he testified with many other arguments and exhorted them, saying, “Save yourselves from this corrupt generation.” So those who welcomed his message were baptized, and that day about three thousand persons were added."

A fantastic quote on baptism as death by St John Chrysostom, From his "Instructions to Catechumens"

"As therefore any one who takes and recasts a golden statue which has been tarnished by time, smoke, dust, rust, restores it to us thoroughly cleansed and glistening: so too this nature of ours, rusted with the rust of sin, and having gathered much smoke from our faults, and having lost its beauty, which He had from the beginning bestowed upon it from himself, God has taken and cast anew, and throwing it into the waters as into a mould, and instead of fire sending forth the grace of the Spirit, then brings us forth with much brightness, renewed, and made afresh, to rival the beams of the sun, having crushed the old man, and having fashioned a new man, more brilliant than the former.

And speaking darkly of this crushing, and this mystic cleansing, the prophet of old said, "You shall dash them in pieces like a potter's vessel."