It looks airtight in most English translations, but it actually comes down to a single comma — one that Jesus didn’t put there, since the earliest Greek manuscripts had no punctuation at all. Translators added it later, and where they place it changes the meaning: "today you will be with me in paradise," or just as validly, "I say to you today, you will be with me in paradise."

The reason that comma matters so much is that we can check the answer against what actually happened over the next three days. If Jesus meant the thief would be with Him in paradise that very day, then Jesus Himself would have needed to be in paradise that day too — but He wasn’t. His body was in the tomb (Matthew 12:40), and on resurrection morning, three days later, He told Mary plainly, "touch me not; for I am not yet ascended to my Father" (John 20:17). If Jesus hadn’t even ascended to His Father three days after the crucifixion, He couldn’t have taken the thief to paradise on the day He said it.

Read the other way, the promise still stands, and stands stronger: "I say to you today" — in this very moment, hanging on a cross, dying as a criminal, seemingly without hope — "you will be with me in paradise." It’s a promise of certain future inclusion in the kingdom, matching what the thief actually asked for just one verse earlier: "remember me when thou comest into thy kingdom" (Luke 23:42) — a request about the future coming of the kingdom, not an ask for an immediate trip to heaven. Jesus answers the request the thief actually made, with a promise that holds together with everything else Scripture says about the dead resting until the resurrection.