I have discussed the salvific efficacy of (water) baptism in many posts on my blog, including two posts dedicated to Acts 2:38:
A lot of ink has been spilt by proponents of the purely symbolic view of baptism on the preposition εις (into/for/with a goal towards), arguing (falsely) that in Acts 2:38, it means that one is baptised as a result of having their sins remitted prior to baptism. I would recommend pursuing the two blog posts linked above that shows that there is no meaningful grammatical and exegetical basis for this contorted interpretation of the text.
That scholarly grammarians agree with the "traditional" rendering of the preposition in Acts 2:38 are numerous; in perhaps the most scholarly Koine Greek lexicon on the market (A Greek-English Lexicon of the New Testament and Other Early Christian Literature [BDAG]), the following definition of εις is offered, with Acts 2:38 being an example of the preposition carrying the meaning with "into" or "with a goal towards" (within the context of Acts 2:38, one is baptised into/with a goal towards a remission of sins, supporting baptism being salvific, not merely symbolic [emphasis added]):
f. to denote purpose in order to, to (Appian, Liby. 101 §476 ἐς ἔκπληξιν=in order to frighten; Just., A I, 21, 4 εἰς προτροπήν ‘to spur on’) εἰς ἄγραν in order to catch someth. Lk 5:4. εἰς ἀπάντησιν, συνάντησιν, ὑπάντησίν τινι (s. these 3 entries) to meet someone, toward someone Mt 8:34; 25:1; J 12:13. εἰς μαρτύριον αὐτοῖς as a witness, i.e. proof, to them Mt 8:4; 10:18; 24:14 al. εἰς ἄφεσιν ἁμαρτιῶν for forgiveness of sins, so that sins might be forgiven Mt 26:28; cp. Mk 1:4; Lk 3:3; Ac 2:38. εἰς μνημόσυνόν τινος in memory of someone Mt 26:13; Mk 14:9; cp. Lk 22:19 al. (εἰς μνημόσυνον En 99:3). εἰς ὅ for which purpose (Hdt. 2, 103, 1) Col 1:29; otherw. 2 Th 1:11 with this in view; εἰς τί; why? (Wsd 4:17; Sir 39:16, 21) Mt 14:31; Mk 14:4; 15:34; Hm 2:5; D 1:5. εἰς τοῦτο for this reason or purpose Mk 1:38; Lk 4:43 v.l.; J 18:37; Ac 9:21; 26:16; Ro 9:17; 14:9; 2 Cor 2:9; 1J 3:8; Hs 1:9 (Just., A I, 13, 3). εἰς αὐτὸ τοῦτο for this very reason 2 Cor 5:5; Eph 6:22; Col 4:8. W. subst. inf. foll. (X., Ages. 9, 3, Mem. 3, 6, 2; Just., A I, 9, 5) in order to (oft. LXX; neg. μή in order not to; s. B-D-F §402, 2) Mt 20:19; 26:2; 27:31; Mk 14:55 and oft.—εἰς ὁδόν for the journey 6:8.
