This announcement prompted the disciples to voice their confusion again (cf. John 13:36; John 14:5; John 14:8; John 14:22), though this time they kept quizzing (Gr. imperfect tense) one another rather than Jesus. They still did not understand what He meant by His departure (cf. John 16:12). Evidently they did grasp that Jesus had been talking about returning to His Father ( John 14:28), but how could He do that and then reappear in a little while?[source]
Jesus" references to "a little while" especially perplexed them ( John 16:18). The fact that John recorded the repetition of "a little while" five times in these three verses shows that he regarded it as very significant. [source][source][source]