Who appeared in glory, and spake of his decease which he should accomplish at Jerusalem.
Note 1 at Lu 9:31: Only Luke mentioned what Moses and Elijah spoke to Jesus about. It can be certain that this was more than a casual conversation. Apparently, they were sharing some details of Jesus' death with Him. Jesus was their Creator (Col 1:16), and yet He humbled Himself and took the form of a man (Php 2:6-7) and had to grow in wisdom (see note 1 at Lu 2:52). This could be a factor in Jesus only mentioning His death four times in the three years prior to this but ten times in the six months following.