A.T. Robertson Commentary Mark 13:34

"[It is] as [when] a man, sojourning in another country, having left his house, and given authority to his servants, to each one his work, commanded also the porter to watch." — Mark 13:34 (ASV)

Commanded also the porter to watch (κα τω θυρωρω ενετειλατο ινα γρηγορη). The porter or door-keeper (θυρωρος), as well as all the rest, to keep a watch (present subjunctive, γρηγορη). This Parable of the Porter is only in Mark. Our ignorance of the time of the Master's return is an argument not for indifference nor for fanaticism, but for alertness and eager readiness for his coming.