The peace Jesus is talking about is not the cessation of hostilities from enemies, but rather the gift of calmness and confidence that comes from union with God and faith in him and his purposes. The world's idea of peace is something that comes through destroying of enemies and consists of physical and emotional comfort. The peace that Jesus gives is grounded in God and not in circumstances. It is the peace that Jesus himself has exhibited in this Gospel and is exhibiting in this farewell discourse, even while he knows he is about to be killed. Soon he will speak of the continued trouble his disciples will experience in the world (15:18--16:4), but they will simply be living out what he himself has already been experiencing. They will share his troubles, but they will also have his peace, for they will share in his own relationship with the Father.
This promise of the gift of his own peace serves as the foundation for the command he now gives: Do not let your hearts be troubled and do not be afraid (v. 27). He repeats exactly the command that began this chapter (v. 1), adding now a reference to fear (mede deiliato). This word family is always used of fear in a negative sense, as the opposite of courage. Those with a settled disposition of such fear evidence a lack of faith in God and a denial of his presence, his goodness and his power. Those who experience such fear, which includes virtually all of us to some degree, may take comfort that as God's life grows within us and as our hearts are healed, we enter into the inheritance of Jesus' peace, which replaces our sinful fear. Jesus here calls us to receive his peace. The grounds of this peace is the "perfect love" that "drives out fear" (1 Jn 4:18). This love is ultimately a sharing of the relationship between the Father and the Son, of which Jesus now goes on to speak.