The shorter form of the gospel in 12:35-40 presents a very strange teaching that would surely have brought smiles all round, if not outright laughter, from its earliest hearers. The word picture that Luke paints is simply not credible in a first century setting where slavery was taken for granted and where the respective roles of masters and slaves were characterised more by extreme violence than by mutuality of any sort. The disciples are told to be like slaves who keep vigil all night long as they await the return of their master from a wedding banquet. Their function is to open the door when he knocks and if they are awake enough to perform this function, there will be an extraordinary reversal of roles: the slaves will sit down at table while the master assumes the role of slave and serves their meal.
The disciples are being prepared for Jesus’ announcement later in the narrative that he is among them as one who serves. They need to understand that something extraordinary is happening, even more extraordinary than the slave-master banquet scenario might suggest. God’s way of being in the world is full of healing experiences and life-enhancing surprises. The final verses of the shorter reading shift to the image of the thief in the night. They are also about vigilance, being watchful and alert so as not to be taken by surprise in the final reckoning.