You know what time it is, how it is now the moment for you to wake from sleep. For salvation is nearer to us now than when we became believers; 12the night is far gone, the day is near. Let us then lay aside the works of darkness and put on the armor of light; 13let us live honorably as in the day, not in reveling and drunkenness, not in debauchery and licentiousness, not in quarreling and jealousy. 14Instead, put on the Lord Jesus Christ, and make no provision for the flesh, to gratify its desires.
When I was a teen, my Sunday school class/youth group was asked to design an altar hanging for Advent. It ended up being very simple: large dark golden letters spelled out “Sleepers, awake” with a Chi Rho against a purple background. This thing could easily be read from the back of the nave, and captured the main idea: that Advent is often described as a time of watchfulness, of anticipation, or preparation. It is a time of waking up and preparing for the coming of Christ.
Our reading from Romans also reminds us to get up and clothe ourselves in the armor of light rather than build up the works of darkness described in verse 13 (reveling, drunkenness, debauchery, licentiousness, quarreling, jealousy). That armor is actually to clothe ourselves in Jesus, to center our thoughts on true discipleship and obedience rather than self-gratification (v. 14).