Hebrews 6:1-2 lists the "principles of the doctrine of Christ." KJV
other versions call them:
"the elementary teachings about Christ" NIV
"the elementary teaching about the Christ" NASB
"the preschool fingerpainting exercises on Christ" The Message
"the basic teachings about Christ" NLT
"the elementary principles of Christ" NKJV
"the elementary stage in the teachings and doctrine of Christ" Amplified
These 6 basic or fundamental doctrines are listed as:
repentance from dead works
faith toward God
baptisms (plural)
laying on of hands
resurrection of the dead
eternal judgment
Notice that baptisms is plural.
Both water baptism and Spirit baptism were part of the experience of the early church.
Baptism/mikveh/ritual cleansing were practiced by the Jews prior to the birth of Christ. These were done by immersion or by the pouring of water. When Jewish people came to John the Baptizer at the Jordan River, he told them that there was another baptism to come, a baptism administered by someone who was greater than he (John) because this Greater One existed before him (even though He was born 6 months after him). This second baptism would be done with or in the Holy Spirit just like their baptism had been done with or in water.
There are about 20 incidents of people being converted or being saved recorded in the Book of Acts and several times it is also stated that these converts or new believers were baptized in water and in the Spirit. Both water and Spirit baptism are recorded as late as the 19th chapter of Acts (verses 1-7)which is considered to have taken place in October AD 53 which is about 20 years after the resurrection of Jesus.