Q: In Luke 23:43, Jesus tells the good thief: "Truly, I say to you, today you will be with me in paradise." Does this mean he went to heaven on Good Friday?A: No. There are a couple of ways of taking this verse. How it is taken depends on whether the temporal clause "today" (Greek, semeron) modifies what comes before it or what comes after it in the sentence. There is no punctuation in the original Greek--all of that is added by the translators--and the sentence can be punctuated one of two basic ways with regard to the word "today," depending on which part of the sentence "today" is supposed to modify. The two basic ways of punctuating it are:
1. Truly, I say to you, "Today you will be with me in paradise."
2. Truly, I say to you today, "You will be with me in paradise."
I have added quotation marks to the promise Jesus is making in order to make the distinction of meaning clearer, but the important thing is the position of the comma. If the comma comes before "today" then Jesus is promising the thief he will be in paradise that day. If the comma comes after today then Jesus is emphatically calling attention to when the promise is made ("today"), but what he is promising is that the thief will end up in paradise and not saying anything about when the thief will end up there. Either one of these is possible given the Greek grammar.
If the first is taken then we must conclude that paradise was where Jesus went when he died. Since he did not go to heaven when he died, but rather he descended to the dead (1 Peter 4:6), paradise at that time would have been in the place of the righteous dead, which at that time was not in heaven but was a place Jesus' described as "Abraham's bosom" (Luke 16:22). The righteous dead only began going to heaven itself after Jesus opened the gate of heaven to them with his resurrection (CCC 632-635, 1026). For the same reason, we can infer paradise was in "Abraham's bosom" rather than heaven at the time since the good thief would not have gone toheaven as Jesus had not yet opened heaven to the righteous dead.
This speculation is unnecessary, however, if the second interpretation of the sentence is taken and Jesus is simply using the word "today" to emphatically call attention to the promise rather than as a part of the promise.