I wish my Christian brethren would give up on this "thief on the cross" argument. It is a horrible argument to make for these reasons:
1. Yes salvation is by faith in Jesus. But not that Jesus is or even that he is God. It is by faith in a very specific thing.
2. That thing is the gospel message (I Cor 15:1-4)
3. The gospel is that "Jesus died for our sins, was buried, and rose again"
4. Faith/Salvation in the church age/Christian era requires believe in those 3 things (death for my sins, burial, resurrection).
5. The thief on the cross did not believe any of those 3 parts of the gospel as none of them had even happened yet.
6. Yes the thief on the cross was saved by faith but the faith of the Old Testament Theology/era/dispensation. There was no baptism as part of the Old Testament (Jewish) salvation/theology. The bible says "Abraham believed God and it was counted to him as righteousness" (note - this was before his circumcision - Paul makes a huge point about this in the whole chapter of Romans 4).
7. Baptism is part of the New Testament/Christian/Church age theology and in EVERY single case in the bible was administered after faith/belief in the gospel. Also in every case in the Bible it was done immediately after belief (not weeks, months, etc. later - it is a travesty to make people go through a 13 week membership class before they can be baptised).
The thief on the cross has nothing to do with the baptism arguments/studies.
It's still the faith that saves, that results in the spirit baptism. It's not the water baptism that saves, it's merely a sign of obedience.
And if you not my last post on this thread, I misread Haole's post, who in a sense had agreed with me.
The thief could have understood from the Old Testament that Jesus would die and redeem many and be resurrected.
Somehow the thief knew both that Jesus was Lord and was going to come into His kingdom and had faith that He would have mercy on Him despite that they were both dying. Jesus answer also confirmed to the man that he was headed for Paradise.
The point of Romans 4 is that it's faith that saves both in the Old Testament and new. Paul doesn't even mention baptism until chapter 6.