Luke 24:17
Then Jesus said to them, "What have you been talking about while [you were] walking along together?" And they stopped [suddenly], looking dejected.
John 16:6
And now that I have told you these things, your hearts are full of grief.
John 16:20-22
Truly, truly, I tell you, you will cry and mourn [i.e., over my suffering and death], but the world will be glad [about it]. You will be sad, but your sadness will turn to joy [i.e., when learning of my resurrection].
Treasury of Scripture Knowledge
Summary
And he said unto them, What manner of communications are these that ye have one to another, as ye walk, and are sad?