The new Jerusalem described in the Letter to the Hebrews is the end of the Christian's journey which takes place along with an awareness of the judgement of God, and of Jesus to whom the privilege should not be treated lightly.
Jesus' instructions to the disciples before sending them out on their mission begins with the negative - "Nothing for the journey, no bread, no haversack, no coppers for their purses" (Mk.6:8). These conditions are to make it clear that any results achieved are not because of human means. "No bread" here is doubly significant because Jesus Himself will feed the crowds with bread, and He will be their bread. His instructions are explicit, depending on the reception given or denied them.
Mark's account ends with the positive results of the mission - the conversion of minds and hearts, the expelling of demons, and the curing of the sick, all of which are extensions of Jesus' own mission. However, the establishing of God's Kingdom, of the new Jerusalem mentioned in Hebrews, can only be done by Jesus Himself, who 'brings a new Covenant, and a blood for purification' (Heb. 12:24).
Lord, we need to 'mission' too. We need to tell others the story of Jesus and our experiences of Jesus; we need to enact this story of Jesus in our daily living as our good news. Amen.