Was Jesus in paradise on the day he died, though on Easter morning he had not yet ascended?

The two sayings are about different things. In Luke 23:43 Jesus speaks of where he and the thief would be when they died that day: their bodies would lie dead, but they themselves, in spirit, would be together in paradise. Jesus’ last words in Luke say the same: “Father, into thy hands I commend my spirit” (Luke 23:46). Paul speaks of being caught up “into paradise” in the same breath as “the third heaven” (2 Corinthians 12:2–4), and Revelation of “the paradise of God” (Revelation 2:7).

In John 20:17 Jesus is speaking after his resurrection, in his risen body, and ‘ascend’ refers to the ascension: his bodily going up to the Father forty days later (Acts 1:9–11; compare John 6:62). Mary seems to have taken hold of him (the BSB has “Do not cling to Me”); Jesus tells her that there is no need to cling to him as though he were about to vanish, because he has not yet ascended, and he sends her to tell the disciples, “I ascend unto my Father, and your Father”. He is not saying that his spirit had not been with the Father between his death and his rising.

So there is no clash. On the Friday the dying Jesus went in spirit to paradise, and the thief with him; on the Sunday the risen Jesus had not yet made his bodily ascension.

Paradise as the place of the righteous dead

Many Christians, in the early church and since, have understood ‘paradise’ here as the blessed part of the realm of the dead, called ‘Abraham’s bosom’ in Luke 16:22, where the righteous waited, and have linked it with Peter’s words that Jesus’ soul was not left in Hades (Acts 2:27, 31). On this view too Jesus was in paradise on the Friday, while his ascension to the Father was still to come.

The comma after ‘today’

Some read Luke 23:43 as ‘I say unto thee today, thou shalt be with me in paradise’, taking ‘today’ with ‘I say’. The earliest manuscripts have little or no punctuation, so this is possible grammatically, but most scholars reject it: wherever else Jesus uses the solemn formula ‘Verily I say unto thee’, it stands on its own and what follows is the content of the saying.