Some argue that the phrase, “be baptized … for the forgiveness of your sins” (Βαπτισθήτω … εἰς ἄφεσιν τῶν ἁμαρτιῶν) in Acts 2.38 means “be baptized … because you already have the forgiveness of your sins”.  The preposition εἰς (for) is used in Matthew 26.28 in the same Greek sentence structure: “blood … is poured out … for the forgiveness of sins” (αἷμά … ἐκχυννόμενονεἰς ἄφεσιν ἁμαρτιῶν).  If εἰς in Matthew 26.28 means “in order to effect” i.e. Jesus’ blood is poured out in order to effect the forgiveness of sins, then Acts 2.38 must also mean that you are baptised in order to effect the forgiveness of your sins.  Hence, no Bible ever translates Acts 2.38 as “be baptized … because you already have the forgiveness of your sins”.  In some versions, the efficacy of baptism is even more pronounced: “that you may have your sins forgiven” (Williams), “in order to have your sins forgiven” (Goodspeed), “so that you can have” (Phillips), “in order to have your sins forgiven” (GNB), “to have your sins forgiven” (Knox), “then your sins will be forgiven” (REB), “so that your sins may be forgiven” (NRSV).  Further, the preposition εἰς is also used in Romans 10.10: “believes and is justified” (πιστεύεται εἰς δικαιοσύνην).  Similarly, it must mean that you believe in order to effect justification; it cannot mean that you believe because you already have justification.