It’s interesting that the entire last chapter of Luke's Gospel seems dedicated to re-assuring the early Christians by using the example of the disciples immediately after the shock of the Crucifixion. Through the Road to Emmaus and the Appearance in Jerusalem, Luke reminds them that Christ is in their presence even though they don't feel that. It was meant as a spiritual boost as they adjusted to the ups and downs of the first years of the Church. He reminds them that they did great things and will continue to do so because they are guided by the Holy Spirit. In a turbulent world and Church, Jesus still is saying "Peace be with you".