Here is an interesting discussion on the Greek word "eis":
http://www.simplybible.com.au/f340.htm
This is an uncomplicated study of the argument about the Greek word “eis”. in Acts 2:38 does εις mean (1) “in order to receive”, or (2) “because you have received”?
Baptism and the Greek Word “eis”
Here's the text: "Peter said to them, 'Repent and let every one of you be baptized in the name of Jesus Christ, for the forgiveness of sins, and you shall receive the gift of the Holy Spirit' " (Acts 2:38).
Baptism and Ice
No, we are not going to talk about baptism in frigid conditions! The little word “for” in the phrase "for the forgiveness of sins" translates the original Greek word εις, usually pronounced “ice” or “ees”. Just as our English word “for” has many meanings, so too does the Greek word εις . You often hear an argument made from this diversity of meaning. The argument says that in Acts 2:38 the word “for” means “because of”. So the passage is made to say, "Repent and be baptized because of the forgiveness of sins". In other words a person should be baptized not in order to receive forgiveness, but because forgiveness has already taken place, and therefore baptism is not necessary to forgiveness.
Is this argument correct, or is it a misrepresentation of the passage and the little Greek word εις?
1 Repentance and Baptism
First you will notice that Peter does not speak of baptism only, but of both repentance and baptism. "Repent and let every one of you be baptized... for the forgiveness of sins..." (Acts 2:38). If the argument places forgiveness before baptism, it also places forgiveness before repentance. In other words, a person should repent not to receive forgiveness, but because forgiveness has already taken place, and therefore repentance is not necessary to forgiveness.
This would make all the translators wrong who make Peter say, "Repent and return so that your sins may be blotted out" (Acts 3:19). If the argument is correct, then the translators are incorrect. They should make Peter say, “Repent and return because your sins have been be blotted out.”
Of course the translators are right and the argument wrong. No translators render either Acts 2:38 or Acts 3:19 so as to put repentance after forgiveness. Rather, they all put repentance before forgiveness, as a condition of forgiveness. And if Peter has put repentance before forgiveness, that's where he has also put baptism, because he gave both repentance and baptism the same relationship to forgiveness viz "Repent and ...be baptized... for the forgiveness of sins..." (Acts 2:38).
2 Faith and Confession
As a parallel example, take Paul’s statement, "With the heart one believes resulting in righteousness, and with the mouth one confesses resulting in salvation" (Rom 10:10). In the Greek we have "belief εις righteousness... confession εις salvation" (Rom 10:10). All translators render this passage as though a heartfelt and confessed faith leads to justification. In other words salvation is the outcome of a confessed faith. Translators don't render the verse to say that faith and confession are because of salvation, and come after salvation.
3 Baptism and Death
Jesus spoke of his, "blood of the new covenant, shed for many for (εις) the forgiveness of sins" (Mtt 26:28). As we all know, Jesus did not shed his blood because forgiveness had been granted, but so that it could be. This is another instructive parallel to Acts 2:38.
However it is even more instructive to examine how Paul relates baptism to the death of Christ and our death to sin (Rom 6:3-5). First Paul says, "Don't you know that all of us who have been baptized εις Christ Jesus have been baptized εις his death? Therefore we have been buried with him through baptism εις death, so that as Christ was raised from the dead by the glory of the Father, so we too might walk in newness of life" (Rom 6:3-4).
Now in this passage, translators put "into" for εις. If, instead, we put the argued “because of ” for εις, it would make some sort of sense —however it would not in the least help the argument. Why not? Because whether Paul said that baptism is “into” Christ’s death or “because of ” Christ’s death the fact remains that we meet and join Christ’s death and resurrection through baptism. We are "buried with him through baptism... so that we might [rise to] walk in newness of life" (Rom 6:4).
The meaning here is clear. Even if Peter said, "be baptized because of the forgiveness of sins" (Acts 2:38) that would simply mean, “You need forgiveness of sin, and Christ's death is your only hope of it. He was killed so you might live. Through baptism you can meet and join the death of Christ, die to sin, and rise to walk in new life. So be baptized because of this forgiveness now waiting for you.”