The thief was not in a day when atonement had already been made. Atonement was not made until after Christ arose the third day and ascended to the holiest in Heaven.
At any rate, Jesus told the disciples at least 43 days after the thief died to BEGIN preaching repentance and remission of sins in His name at Jerusalem after the received the power from on high, which is Spirit Baptism. And they BEGAN preaching that message on the day of Pentecost in
Acts 2:38. Why preach something else?