When we believe in Jesus.
This is how I see it. That obviously doesn’t make it correct, but I can use scripture to explain it.
“for this is my blood of the new testament, which is shed for many for the remission of sins.”
Matthew 26:28 KJV
https://bible.com/bible/1/mat.26.28.KJV
In this passage “for the remission of sins” is eis aphesin hamartion in Greek. The most common translation of eis is into. So, Jesus blood was poured out into remission of sins. Remission of sins represents the new covenant.
“and that repentance for the forgiveness of sins should be proclaimed in his name to all nations, beginning from Jerusalem.”
Luke 24:47 ESV
https://bible.com/bible/59/luk.24.47.ESV
In this passage we see ”repentance for the remission of sins.” In Greek it is metanoian eis/kai aphesin hamartion. Several of the oldest manuscripts use eis. I see evidence in the Bible that eis is not wrong. This passage illustrates that:
“To him all the prophets bear witness that everyone who believes in him receives forgiveness of sins through his name.””
Acts 10:43 ESV
https://bible.com/bible/59/act.10.43.ESV
To me it seems that Peter is remembering here what Jesus said to the apostles in Luke 24 when he opened their minds to understand the scriptures.
“Then he said to them, “These are my words that I spoke to you while I was still with you, that everything written about me in the Law of Moses and the Prophets and the Psalms must be fulfilled.” Then he opened their minds to understand the Scriptures, and said to them, “Thus it is written, that the Christ should suffer and on the third day rise from the dead, and that repentance for the forgiveness of sins should be proclaimed in his name to all nations, beginning from Jerusalem.”
Luke 24:44-47 ESV
https://bible.com/bible/59/luk.24.45-47.ESV
Metanoia means “a change of mind.” If your mind changes from unbelieving to believing you have simply become a believer In Jesus. So, Acts 10:43 is simply Peter remembering what Jesus taught him in Luke 24. Luke 24 is where Jesus opened his mind to understand the prophets. This would be consistent with the use of eis in Luke 24:47. It also, doesn’t make kai wrong.
This is why I see Luke 24:47 as saying “a change of mind into remission of sins.” or change your mind and be immersed into remission of sins.
“And Peter said to them, “Repent and be baptized every one of you in the name of Jesus Christ for the forgiveness of your sins, and you will receive the gift of the Holy Spirit.”
Acts 2:38 ESV
https://bible.com/bible/59/act.2.38.ESV
If you look at the greek words in Acts 2:38 and consider their meanings, you very simply end up with this:
”Change your mind and be immersed every one of you on (epi) the authority (onomati) of Jesus Christ into (eis) the remission of your sins….” When you change your mind and believe in Jesus you are immersed into remission of sins (the new covenant). Now remember Matthew 26:28, Jesus blood was poured out into (eis) remission of sins. So its not a water immersion, its an immersion into the new covenant, into remission of sins, into Jesus blood.
When you are immersed into remission of sins upon a change of mind, you are immersed into Jesus’ blood.
Also, think about other ways you see this in scripture such as immersed into his death or immersed into Christ. If you are immersed into his blood all of these are true as well. We have been buried with him or immersed into his death (blood).
Think about the similarity between this immersion and the immersion of the Israelites into Moses in 1 Corinthians 10:2.