The interpretation of this verse depends entirely on punctuation, which rests wholly on human authority, the Greek manuscripts having no punctuation of any kind till the ninth century, and then it is only a dot (in the middle of the line) separating each word. See Appendix 94, V. i. 3.
  The Verb "to say", when followed by hoti, introduces the ipsissima verba of what is said; and answers to our quotation marks. So here (in Luke 23:43), in the absence of hoti = "that", there may be a doubt as to the actual words included in the dependent clause. But the doubt is resolved (1) by the common Hebrew idiom, "I say unto thee this day", which is constantly used for very solemn emphasis (see note on Deuteronomy 4:26); as well as (2) by the usage observable in other passages where the verb is connected with the Greek semeron = to-day.

 1.  With hoti:—
  Mark 14:30: "Verily I say unto thee, that (hoti) 'this day . . . thou shalt deny me thrice.'"
  Luke 4:21: "And He began to say unto them, that (hoti) 'This day is this scripture fulfilled in your ears.'"
  Luke 5:26: "Saying (hoti = that), 'We have seen strange things to-day.'"
  Luke 19:9: "Jesus said unto him that (hoti), 'This day is salvation come to this house.'"
  For other examples of the verb "to say", followed by hoti, but not connected with semeron (to-day), see Matthew 14:26; 16:18; 21:3; 26:34; 27:47. Mark 1:40; 6:14, 15, 18, 35; 9:26; 14:25. Luke 4:24, 41; 15:27; 17:10; 19:7.

 2.  Without hoti:—
  On the other hand, in the absence of hoti (= that), the relation of the word "to-day" must be determined by the context.
  Luke 22:34: "And He said, 'I tell thee, Peter, in no wise shall a cock crow to-day before thou shalt thrice deny that thou knowest Me.'" Here the word "to-day" is connected with the verb "crow", because the context requires it. Compare Hebrews 4:7.

  It is the same in Luke 23:43: "And Jesus said to him, 'Verily I say unto thee to-day [or this day,¹ when, though they were about to die, this man had expressed so great faith in Messiah's coming Kingdom, and therefore in the Lord's resurrection to be its King—now, under such solemn circumstances] thou shalt be, with Me, in Paradise.'" For, when Messiah shall reign, His Kingdom will convert the promised land into a Paradise. Read Isaiah 35, and see note on Ecclesiastes 2:5.

  We must notice also the Article before "Paradise". It is "THE Paradise", namely the paradise of which the prophets tell in such glowing language, when the Lord shall come in His Kingdom. See Psalms 67:4, 6; 72:6, 7, 16, 17. Isaiah 4:2; 30:23, 24; 35:1, 2, 5, 6; 41:18, 20. Jeremiah 31:5, 12. Ezekiel 34:25-27; 36:29, 30; 47:8, 9, 12. Hosea 2:18, 21, 22. Joel 3:18. Amos 9:13-15. Zech. 8:12.

  It has no connection with Babylonian, Jewish, and Romish tradition, but is a direct answer to the malefactor's prayer. His prayer referred to the Lord's coming and His Kingdom; and, if the Lord's answer was direct, the promise must have referred to that coming and to that Kingdom, and not to anything that was to happen on the day on which the words were being spoken.

  It is alleged that the Lord's promise was a reply to the man's thought; but this is an assumption for which no justification can be found. Moreover, how can we know what his thought was, except by the words he uttered?

  The Lewis Codex of the Syrian New Testament reads in verse 39: "save Thyself and us to-day". So the Lord's word "to-day" may have reference to the revilings of the one, as well as to the request of the other.
  
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  ¹ It is rendered "to-day" eighteen times in the Gospels, Hebrews and James; but "this day" twenty-three times (five times in Matthew; once in Mark; four times in Luke; nine times in Acts; once in Romans; twice in 2Corinthians; and once in Hebrews).