Note 2 at Lu 12:35: This phrase, "let your loins be girded about," is a reference to being prepared. In Jesus' time people wore long, loose-fitting robes that could get in the way if they were running or preparing to fight. Therefore, men would grab the bottom of these robes in the back and pull them up between their legs and tuck them in their girdles (or belts). This was called "girding up your loins" and prepared them for fight or flight.

Jesus had just spoken about covetousness and its snares (Lu 12:13-34), and His meaning here is to be prepared for the soon return of your master. "Don't be in the relaxed position that riches can lull you into (De 6:10-12, 8:10-11; Mt 6:24, 19:23-24; Mr 4:19; and 1Ti 6:9-10), but be watching for the Lord's return."

The next phrase, "and your lights burning," is making the same point about being prepared and parallels the parable of Mt 25:1-13. Both phrases are teaching us to stay ready and not leave anything that would have to be done and possibly cause us to miss our Lord's return.