Take no thought for your life, what ye shall eat; neither for the body, what ye shall put on. 12:22
Why would they do that? Well, the Governing Body doesn't believe in a soul, so they say the good thief died like everyone else. Only later, nearly 2000 years later, after Armageddon, would he be resurrected. So they couldn't let Jesus tell him that he'd be with him that very day in paradise. Instead, they have Jesus say that he is telling the truth today (Not yesterday or tomorrow, but today. Or maybe "today" here is emphasizing that he's telling the truth today, but he was lying yesterday or something) -- and that sometime in the far distant future they'd be together in paradise. 23:43