Advent is a season of waiting. In this season we are reminded of how the Jews were waiting for a Messiah, or in the words of Anna in the temple, waiting for the consolation or redemption of Israel (Luke 2:28).
We reflect this waiting when we sing O Come, O Come Emmanuel, and ransom captive Israel.
In a similar way now, Christians are waiting for the second advent/coming of Jesus. Advent is a good time to talk about the second advent of Jesus.
It is also appropriate to talk about the second advent of Jesus at advent because the first advent set in motion all the events that lead to the second advent. The two are closely connected. You can’t have one without the other. The first advent will be completed at the second advent.
At the first advent Satan poured all His energy into trying to defeat Jesus. Killing the babies in Bethlehem, trying to trip Jesus up at His temptation, the betrayal of Judas, killing Jesus on the cross. After Jesus’ resurrection and ascension, Satan is focusing all his energy on the body of Christ, the church. But know this, Satan is bound and defeated and doomed. Jesus promised that though there would be trials and afflictions the gates of hell would not and will never prevail.
By bound we understand Scripture to mean he is limited, it is as if he is on a leash.