John Gill Commentary Luke 24:38

"And he said unto them, Why are ye troubled? and wherefore do questionings arise in your heart?" — Luke 24:38 (ASV)

And he said to them, why are you troubled Who had more reason to rejoice, and be glad, as they were when they knew that it was Jesus: and why do thoughts arise in your hearts ?

whether what they saw was Jesus, or an apparition, which gave them a great deal of trouble and uneasiness, and filled them with fright and terror; as it was, and is usual with persons when they fancy they see a spirit, or an apparition; see (Matthew 14:26) .