• The thief was saved without Water Baptism. so does that mean it is not necessary?

When discussing salvation, many times the thief on the cross comes up.  Even folks with little knowledge about the Bible know about the thief on the cross. This can lead into  the belief that we do not have to obey the teaching of water baptism given to us in the great commission.  Matt 28:19, Luke 24:47, Mark 16:16.  And that New Testament Salvation is apart from Water Baptism. But what does the Bible teach?   

• Jesus Christ had the authority to forgive sins on earth.

To understand this answer, we must understand that Jesus Christ came to be the Lamb of God.  Serving as the High Priest for all of mankind, Jesus Christ shed the necessary blood for the remission of sins. Hebrews 9:22.   Because Jesus Christ was the High Priest, and because He would be the "one mediator between heaven and earth." While Jesus Christ was on earth, He had the authority to forgive sins on earth Mark 2:10, Luke 5:24.  This extends simply until the day of Pentecost when men would have to be born again, for Jesus came back as the Holy Ghost and gave them the overcoming power to live above sin. 1 John 3:9 Romans 6:1-6. The only way for us to receive that blood after Pentecost is to be born of the water and Spirit. John 3:5, 1 John 5:8, Acts 2:38.

• Water Baptism was NOT a teaching of the Law but of Grace.

The fact is that the thief died under the law.  The Holy Ghost had not yet fallen for Jesus had not ascended.  John 7:39  Water baptism is not a part of the law, it was introduced by John the Baptist for the remission of sins. Mark 1:4, Luke 3:3  Therefore to say that water baptism was a part of the law is erroneous.  So if that was not part of the law, then what would it take for a sinner, like the thief, to be forgiven in the law?  Any student of the Old Testament knows the answer to this, he needed a blood sacrifice. He needed to take it to the High Priest and the High Priest would act as that "intercessor" which would bring the blood into the Holy Place, and the glory of God would fall and atonement would be made.

• The thief was living in the time of the Law, before Pentecost. Water Baptism and Spirit Baptism had not been given until Pentecost.

The point is that the thief along with the Old Testament saints were saved by obedience to the law When Christ was crucified His blood covered the obedient people of the Old Covenant. When the thief was ready to repent, he would need to take a sacrifice to the high priest. But since he was tied to a wood cross (tree), he could not get to a sacrifice.  Therefore the mercy of God was with him, and Jesus Christ right there at Calvary became his High Priest, and  his Sacrifice.  Remember it was after the resurrection that Christ gave the great commission, and the Spirit was not yet fallen until the day of Pentecost. John 7:39. Therefore the only plan of salvation after Pentecost is as it was when it was unlocked by the man with the keys to the kingdom, Simon Peter,

Acts:2:38
"Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost. "