Why in John 20:17 did Jesus say “Do not cling to me, for I have not yet ascended to the Father; but go to my brothers and say to them, ‘I am ascending to my Father and your Father, to my God and your God.’” If Jesus had not yet ascended to the Father, how could He have committed His Spirit to the Father?

On the day that Jesus died on the cross, Jesus’ spirit went to be with the Father (Luke 23:46). So it was his spirit that had been with the Father, but his physical body had not yet ascended into heaven at the time he had spoken to Mary. The bodily ascension is what took place about 40 days later (Acts 1:3, 9-10).